IB/srp: Test only once whether iu allocation succeeded

Merge the two tests in srp_queuecommand() of whether information unit
allocation succeeded into one.  An intended side effect of this change
is that we fix the warning:

    drivers/infiniband/ulp/srp/ib_srp.c: In function 'srp_queuecommand':
    drivers/infiniband/ulp/srp/ib_srp.c:1116: warning: 'req' may be used uninitialized in this function

(seen with CONFIG_CC_OPTIMIZE_FOR_SIZE=y at least with gcc 4.4.4)
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: David Dillow <dillowda@ornl.gov>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/ulp/srp/ib_srp.c

@@ -1132,15 +1132,12 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 
 	spin_lock_irqsave(&target->lock, flags);
 	iu = __srp_get_tx_iu(target, SRP_IU_CMD);
-	if (iu) {
-		req = list_first_entry(&target->free_reqs, struct srp_request,
-				      list);
-		list_del(&req->list);
-	}
-	spin_unlock_irqrestore(&target->lock, flags);
-
 	if (!iu)
-		goto err;
+		goto err_unlock;
+
+	req = list_first_entry(&target->free_reqs, struct srp_request, list);
+	list_del(&req->list);
+	spin_unlock_irqrestore(&target->lock, flags);
 
 	dev = target->srp_host->srp_dev->dev;
 	ib_dma_sync_single_for_cpu(dev, iu->dma, srp_max_iu_len,
@@ -1185,6 +1182,8 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
 
 	spin_lock_irqsave(&target->lock, flags);
 	list_add(&req->list, &target->free_reqs);
+
+err_unlock:
 	spin_unlock_irqrestore(&target->lock, flags);
 
 err: