bind bsg to all SCSI devices

This patch binds bsg to all SCSI devices (their request queues) like
the current sg driver does. We can send SCSI commands to non disk and
cdrom scsi devices like OSD via bsg.

This patch removes bsg_register_queue from blk_register_queue so bsg
devices aren't bound to non SCSI block devices. If they want bsg, I'll
send a patch to do that.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>