This patch avoids that gcc reports the following warning when
building with W=1:

drivers/scsi/scsi_debug.c:2264:15: warning: variable ?pcontrol? set but not used [-Wunused-but-set-variable]
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>