The setup of MSI with Hyper-V host was sleeping with locks held.  This
error is reported when doing SR-IOV hotplug with kernel built with lockdep:

    BUG: sleeping function called from invalid context at kernel/sched/completion.c:93
    in_atomic(): 1, irqs_disabled(): 1, pid: 1405, name: ip
    3 locks held by ip/1405:
   #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff976b10bb>] rtnetlink_rcv+0x1b/0x40
   #1:  (&desc->request_mutex){+.+...}, at: [<ffffffff970ddd33>] __setup_irq+0xb3/0x720
   #2:  (&irq_desc_lock_class){-.-...}, at: [<ffffffff970ddd65>] __setup_irq+0xe5/0x720
   irq event stamp: 3476
   hardirqs last  enabled at (3475): [<ffffffff971b3005>] get_page_from_freelist+0x225/0xc90
   hardirqs last disabled at (3476): [<ffffffff978024e7>] _raw_spin_lock_irqsave+0x27/0x90
   softirqs last  enabled at (2446): [<ffffffffc05ef0b0>] ixgbevf_configure+0x380/0x7c0 [ixgbevf]
   softirqs last disabled at (2444): [<ffffffffc05ef08d>] ixgbevf_configure+0x35d/0x7c0 [ixgbevf]

The workaround is to poll for host response instead of blocking on
completion.
Signed-off-by: NStephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>