[media] lirc: fix non-ANSI function declaration warning

Sparse is warning about non-ANSI function declaration.
Add void to the parameterless function.

drivers/staging/media/lirc/lirc_bt829.c:174:22: warning:
	non-ANSI function declaration of function 'poll_main'
Signed-off-by: Emil Goode <emilgoode@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/staging/media/lirc/lirc_bt829.c

@@ -171,7 +171,7 @@ static void cycle_delay(int cycle)
 }
 
 
-static int poll_main()
+static int poll_main(void)
 {
 	unsigned char status_high, status_low;