[PATCH] cleanup cdrom_ioctl

Add a small helper for each ioctl to cut down cdrom_ioctl to a readable
size.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Acked-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Benoit Boissinot <benoit.boissinot@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>