net/mlx5: Fix uninitialized variable bug in outlen_write()

If sscanf() return 0, outlen is uninitialized and used in kzalloc(),
this is unexpected. We should return -EINVAL if the string is invalid.

Fixes: e126ba97 ("mlx5: Add driver for Mellanox Connect-IB adapters")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/cmd.c

@@ -1497,8 +1497,8 @@ static ssize_t outlen_write(struct file *filp, const char __user *buf,
 		return -EFAULT;
 
 	err = sscanf(outlen_str, "%d", &outlen);
-	if (err < 0)
-		return err;
+	if (err != 1)
+		return -EINVAL;
 
 	ptr = kzalloc(outlen, GFP_KERNEL);
 	if (!ptr)