mb/asus/p8z77-m[_pro]: Blink power LED during suspend

Set GPIO27 of PCH to blink before going to sleep. This blinks the
power LED. Revert after waking up.

Tested on p8z77-m. Power LED blinks in suspend.

Change-Id: Ie1b40ae17fa2ef397585b86ac82730099b611dda
Signed-off-by: Keith Hui <buurin@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81923
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <patrick.rudolph@9elements.com>

src/mainboard/asus/p8x7x-series/acpi/platform.asl

@@ -2,9 +2,19 @@
 
 Method(_PTS, 1)
 {
+#if (CONFIG(BOARD_ASUS_P8Z77_M) || CONFIG(BOARD_ASUS_P8Z77_M_PRO))
+	/* blink power LED if not turning off */
+	If (Arg0 != 0x05)
+	{
+	    GB27 = 1
+	}
+#endif
 }
 
 Method(_WAK, 1)
 {
+#if (CONFIG(BOARD_ASUS_P8Z77_M) || CONFIG(BOARD_ASUS_P8Z77_M_PRO))
+	GB27 = 0
+#endif
 	Return(Package(){0, 0})
 }