[media] rc-main: store_filter: pass errors to userland

Propagate errors returned by drivers from the s_filter callback back to
userland when updating scancode filters. This allows userland to see
when the filter couldn't be updated, usually because it's not a valid
filter for the hardware.

Previously the filter was being updated conditionally on success of
s_filter, but the write always reported success back to userland.
Reported-by: Antti Seppälä <a.seppala@gmail.com>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/rc/rc-main.c

@@ -1090,7 +1090,7 @@ static ssize_t store_filter(struct device *device,
 
 unlock:
 	mutex_unlock(&dev->lock);
-	return count;
+	return (ret < 0) ? ret : count;
 }
 
 static void rc_dev_release(struct device *device)