mlx5: Fix need_uuar_lock when there are no medium bfregs

Fixes need_uuar_lock() to work properly even when there are no
medium bfregs. At that case bfreg entry 1 gets a wrong value, need lock
instead of not needing a lock.

The above case might happen only if the user uses the environment variable
'MLX5_NUM_LOW_LAT_UUARS' and sets it to be less than tot_uuars by 1,
leaving no available medium bfregs.

Fixes: 8c4791a ("libmlx5: First version of libmlx5")
Reported-by: Rohit Zambre <rzambre@uci.edu>
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>

providers/mlx5/mlx5.c

@@ -555,10 +555,13 @@ static int get_num_low_lat_uuars(int tot_uuars)
  */
 static int need_uuar_lock(struct mlx5_context *ctx, int uuarn)
 {
+	int i;
+
 	if (uuarn == 0 || mlx5_single_threaded)
 		return 0;
 
-	if (uuarn >= (ctx->tot_uuars - ctx->low_lat_uuars) * 2)
+	i = (uuarn / 2) + (uuarn % 2);
+	if (i >= ctx->tot_uuars - ctx->low_lat_uuars)
 		return 0;
 
 	return 1;