Running the contrib/test/test-media script in v4l-utils with the vivid argument
will cause this kernel warning:

[  104.748720] videodev: v4l2_release
[  104.748731] ------------[ cut here ]------------
[  104.748750] DEBUG_LOCKS_WARN_ON(lock->magic != lock)
[  104.748790] WARNING: CPU: 6 PID: 1823 at kernel/locking/mutex.c:938 __mutex_lock+0x919/0xc10
[  104.748800] Modules linked in: rc_cec vivid v4l2_tpg videobuf2_dma_contig cec rc_core v4l2_dv_timings videobuf2_vmalloc videobuf2_memops
videobuf2_v4l2 videobuf2_common videodev mc vmw_balloon vmw_vmci button vmwgfx
[  104.748845] CPU: 6 PID: 1823 Comm: sleep Not tainted 5.4.0-rc1-test-no #150
[  104.748853] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/29/2019
[  104.748867] RIP: 0010:__mutex_lock+0x919/0xc10
[  104.748878] Code: 59 83 e8 9a fc 16 ff 44 8b 05 23 61 38 01 45 85 c0 0f 85 ef f7 ff ff 48 c7 c6 a0 1f 87 82 48 c7 c7 a0 1e 87 82 e8 cd bb
f7 fe <0f> 0b e9 d5 f7 ff ff f6 c3 04 0f 84 3b fd ff ff 49 89 df 41 83 e7
[  104.748886] RSP: 0018:ffff88811a357b80 EFLAGS: 00010286
[  104.748895] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[  104.748902] RDX: 0000000000000003 RSI: 0000000000000004 RDI: ffffed102346af62
[  104.748910] RBP: ffff88811a357cf0 R08: ffffffff81217c91 R09: fffffbfff061c271
[  104.748917] R10: fffffbfff061c270 R11: ffffffff830e1383 R12: ffff8881a46103c0
[  104.748924] R13: 0000000000000000 R14: ffff8881a4614f90 R15: ffff8881a46153d0
[  104.748933] FS:  0000000000000000(0000) GS:ffff8881b6780000(0000) knlGS:0000000000000000
[  104.748940] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  104.748949] CR2: 00007f163fc9ca20 CR3: 0000000003013004 CR4: 00000000001606e0
[  104.749036] Call Trace:
[  104.749051]  ? _raw_spin_unlock+0x1f/0x30
[  104.749067]  ? llist_add_batch+0x33/0x50
[  104.749081]  ? tick_nohz_tick_stopped+0x19/0x30
[  104.749130]  ? v4l2_release.cold+0x6c/0xd6 [videodev]
[  104.749143]  ? mutex_lock_io_nested+0xb80/0xb80
[  104.749153]  ? vprintk_emit+0xf2/0x220
[  104.749191]  ? vivid_req_validate+0x40/0x40 [vivid]
[  104.749201]  ? printk+0xad/0xde
[  104.749211]  ? kmsg_dump_rewind_nolock+0x54/0x54
[  104.749226]  ? locks_remove_file+0x78/0x2b0
[  104.749248]  ? __fsnotify_update_child_dentry_flags.part.0+0x170/0x170
[  104.749281]  ? vivid_req_validate+0x40/0x40 [vivid]
[  104.749321]  ? v4l2_release.cold+0x6c/0xd6 [videodev]
[  104.749361]  v4l2_release.cold+0x6c/0xd6 [videodev]
[  104.749378]  __fput+0x15a/0x390
[  104.749393]  task_work_run+0xb2/0xe0
[  104.749407]  do_exit+0x4d0/0x1200
[  104.749422]  ? do_user_addr_fault+0x367/0x610
[  104.749431]  ? release_task+0x990/0x990
[  104.749449]  ? rwsem_spin_on_owner+0x170/0x170
[  104.749463]  ? vmacache_find+0xb2/0x100
[  104.749476]  do_group_exit+0x85/0x130
[  104.749487]  __x64_sys_exit_group+0x23/0x30
[  104.749500]  do_syscall_64+0x5e/0x1c0
[  104.749511]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  104.749520] RIP: 0033:0x7f163fc5c9d6
[  104.749536] Code: Bad RIP value.
[  104.749543] RSP: 002b:00007ffe6f3bec58 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
[  104.749553] RAX: ffffffffffffffda RBX: 00007f163fd4d760 RCX: 00007f163fc5c9d6
[  104.749560] RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
[  104.749567] RBP: 0000000000000000 R08: 00000000000000e7 R09: ffffffffffffff80
[  104.749574] R10: 00007ffe6f3beb24 R11: 0000000000000246 R12: 00007f163fd4d760
[  104.749581] R13: 0000000000000002 R14: 00007f163fd56428 R15: 0000000000000000
[  104.749597] ---[ end trace 66f20f73fc0daf79 ]---

This is caused by media_device_cleanup() which destroys
v4l2_dev->mdev->req_queue_mutex. But v4l2_release() tries to lock
that mutex after media_device_cleanup() is called.

By moving media_device_cleanup() to the v4l2_device's release function it is
guaranteed that the mutex is valid whenever v4l2_release is called.
Signed-off-by: NHans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab@kernel.org>