[SCSI] qla4xxx: Fix srb lookup in qla4xxx_eh_device_reset

eh_device_reset may be called from scsi error handler or sg_reset, etc.
When called from sg_reset, there will not be an associated srb.  The
driver should lookup the corresponding device handle given information
from the supplied cmd structure and should not assume that there exists
an srb.
Signed-off-by: NKaren Higgins <karen.higgins@qlogic.com>
Signed-off-by: NMike Christie <michaelc@cs.wisc.edu>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>

drivers/scsi/qla4xxx/ql4_os.c

@@ -1543,11 +1543,9 @@ static int qla4xxx_eh_device_reset(struct scsi_cmnd *cmd)
 {
 	struct scsi_qla_host *ha = to_qla_host(cmd->device->host);
 	struct ddb_entry *ddb_entry = cmd->device->hostdata;
-	struct srb *sp;
 	int ret = FAILED, stat;
 
-	sp = (struct srb *) cmd->SCp.ptr;
-	if (!sp || !ddb_entry)
+	if (!ddb_entry)
 		return ret;
 
 	dev_info(&ha->pdev->dev,