mlx4_core: Reserve the correct number of MTT segments

Taking ilog2(dev->caps.reserved_mtts) to find out the order to pass to
the MTT buddy allocator will do the wrong thing if reserved_mtts is ever
not a power of 2.  Be safe and use fls(dev->caps.reserved_mtts - 1).
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/net/mlx4/mr.c

@@ -444,7 +444,7 @@ int __devinit mlx4_init_mr_table(struct mlx4_dev *dev)
 		goto err_buddy;
 
 	if (dev->caps.reserved_mtts) {
-		if (mlx4_alloc_mtt_range(dev, ilog2(dev->caps.reserved_mtts)) == -1) {
+		if (mlx4_alloc_mtt_range(dev, fls(dev->caps.reserved_mtts - 1)) == -1) {
 			mlx4_warn(dev, "MTT table of order %d is too small.\n",
 				  mr_table->mtt_buddy.max_order);
 			err = -ENOMEM;