media: rc-loopback: return number of emitters rather than error

The LIRC_SET_TRANSMITTER_MASK ioctl should return the number of emitters
if an invalid list was set.

Cc: stable@vger.kernel.org
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/rc/rc-loopback.c

@@ -42,7 +42,7 @@ static int loop_set_tx_mask(struct rc_dev *dev, u32 mask)
 
 	if ((mask & (RXMASK_REGULAR | RXMASK_LEARNING)) != mask) {
 		dprintk("invalid tx mask: %u\n", mask);
-		return -EINVAL;
+		return 2;
 	}
 
 	dprintk("setting tx mask: %u\n", mask);