mb/google/beltino/smihandler: Remove 'return' from void function

Change-Id: Iadd8a0f3bae07918990cba8f33eb1e65f4e1977a
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/77188
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/beltino/smihandler.c

@@ -23,5 +23,4 @@ void mainboard_smi_sleep(u8 slp_typ)
 	default:
 		break;
 	}
-	return;
 }