[SCSI] tgt: fix build errors when dprintk is defined

drivers/scsi/ibmvscsi/ibmvstgt.c: In function 'ibmvstgt_cmd_done':
drivers/scsi/ibmvscsi/ibmvstgt.c:292: error: 'cmd' undeclared (first use in this function)
drivers/scsi/ibmvscsi/ibmvstgt.c:292: error: (Each undeclared identifier is reported only once
drivers/scsi/ibmvscsi/ibmvstgt.c:292: error: for each function it appears in.)

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>