media: gspca/sq905.c: fix uninitialized variable

act_len can be uninitialized if usb_bulk_msg() returns an error.
Set it to 0 to avoid a KMSAN error.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reported-by: syzbot+a4e309017a5f3a24c7b3@syzkaller.appspotmail.com
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/usb/gspca/sq905.c

@@ -158,7 +158,7 @@ static int
 sq905_read_data(struct gspca_dev *gspca_dev, u8 *data, int size, int need_lock)
 {
 	int ret;
-	int act_len;
+	int act_len = 0;
 
 	gspca_dev->usb_buf[0] = '\0';
 	if (need_lock)