[PATCH] cdrom: use unsigned bitfields

Fix 23 of these sparse warnings on x86_64 allmodconfig:
include/linux/cdrom.h:942:19: error: dubious bitfield without explicit
`signed' or `unsigned'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>