[media] rainshadow-cec: ensure exit_loop is intialized

exit_loop is not being initialized, so it contains garbage. Ensure it is
initialized to false.

Detected by CoverityScan, CID#1436409 ("Uninitialized scalar variable")

Fixes: ea6a69defd3311 ("[media] rainshadow-cec: avoid -Wmaybe-uninitialized warning")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/usb/rainshadow-cec/rainshadow-cec.c

@@ -119,7 +119,7 @@ static void rain_irq_work_handler(struct work_struct *work)
 
 	while (true) {
 		unsigned long flags;
-		bool exit_loop;
+		bool exit_loop = false;
 		char data;
 
 		spin_lock_irqsave(&rain->buf_lock, flags);