[SCSI] scsi_debug: remove unnecessary function declarations

This patch removes lots of function declarations with moving
scsi_debug_queuecommand. This cleans up scsi_debug_queuecommand a bit
to silence checkpatch.pl
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Douglas Gilbert <dougg@torque.net>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>