[PATCH] cleanup cdrom_ioctl

Add a small helper for each ioctl to cut down cdrom_ioctl to a readable
size.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Cc: Acked-by: Jens Axboe <axboe@suse.de>
Signed-off-by: NBenoit Boissinot <benoit.boissinot@ens-lyon.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>