usb: f_fs: fix ffs_epfile_io returning success on req alloc failure

In the AIO path, if allocating of a request failse, the function simply
goes to the error_lock path whose end result is returning value of ret.
However, at this point ret’s value is zero (assigned as return value from
ffs_mutex_lock).

Fix by adding ‘ret = -ENOMEM’ statement.
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/gadget/function/f_fs.c

@@ -793,8 +793,10 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 
 		if (io_data->aio) {
 			req = usb_ep_alloc_request(ep->ep, GFP_KERNEL);
-			if (unlikely(!req))
+			if (unlikely(!req)) {
+				ret = -ENOMEM;
 				goto error_lock;
+			}
 
 			req->buf      = data;
 			req->length   = data_len;