RDMA/mlx5: no need to kfree NULL pointer

Goto label 'free' where it will kfree the 'in' is not needed though
it's safe to kfree NULL. Return err code directly to simplify the code.

1973 free:
1974         kfree(in);
1975         return err;
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Link: https://lore.kernel.org/r/20221203033714.25870-1-lizhijian@fujitsu.comSigned-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/hw/mlx5/mr.c

@@ -1929,10 +1929,8 @@ int mlx5_ib_alloc_mw(struct ib_mw *ibmw, struct ib_udata *udata)
 	ndescs = req.num_klms ? roundup(req.num_klms, 4) : roundup(1, 4);
 
 	in = kzalloc(inlen, GFP_KERNEL);
-	if (!in) {
-		err = -ENOMEM;
-		goto free;
-	}
+	if (!in)
+		return -ENOMEM;
 
 	mkc = MLX5_ADDR_OF(create_mkey_in, in, memory_key_mkey_entry);