[SCSI] ibmvfc: Fix invalid error response handling

Fix an obvious bug in processing error responses for SCSI commands
which can result in successful responses being incorrectly returned
with DID_ERROR.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>