media: dvb-usb/dvb-usb-urb.c: initialize actlen to 0

This fixes a syzbot failure since actlen could be uninitialized,
but it was still used.

Syzbot link:

https://syzkaller.appspot.com/bug?extid=6bf9606ee955b646c0e1

Reported-and-tested-by: [e-mail]

Signed-off-by: Hans Verkuil <[e-mail]>
Acked-by: Sean Young <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/usb/dvb-usb/dvb-usb-urb.c

···
 int dvb_usb_generic_rw(struct dvb_usb_device *d, u8 *wbuf, u16 wlen, u8 *rbuf,
 	u16 rlen, int delay_ms)
 {
-	int actlen,ret = -ENOMEM;
+	int actlen = 0, ret = -ENOMEM;
 
 	if (!d || wbuf == NULL || wlen == 0)
 		return -EINVAL;