[SCSI] qla2xxx: Check for empty slot in request queue before posting Command type 6 request.

For ISP82xx, the check for empty slot in request queue before posting command type 6
request was missing. This could lead to request queue entry corruptions causing
IO timeouts.
Signed-off-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/qla2xxx/qla_nx.c

@@ -2672,6 +2672,19 @@ qla82xx_start_scsi(srb_t *sp)
 sufficient_dsds:
 		req_cnt = 1;
 
+		if (req->cnt < (req_cnt + 2)) {
+			cnt = (uint16_t)RD_REG_DWORD_RELAXED(
+				&reg->req_q_out[0]);
+			if (req->ring_index < cnt)
+				req->cnt = cnt - req->ring_index;
+			else
+				req->cnt = req->length -
+					(req->ring_index - cnt);
+		}
+
+		if (req->cnt < (req_cnt + 2))
+			goto queuing_error;
+
 		ctx = sp->ctx = mempool_alloc(ha->ctx_mempool, GFP_ATOMIC);
 		if (!sp->ctx) {
 			DEBUG(printk(KERN_INFO