mb/amd/gardenia: Convert to ASL 2.0 syntax

Change-Id: I8c8845ed6eb466acff568247184c6ad6b186e9ec
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46145
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/amd/gardenia/acpi/sleep.asl

@@ -26,10 +26,10 @@ Method(_PTS, 1) {
 	/* DBGO("\n") */
 
 	/* Clear wake status structure. */
-	Store(0, PEWD)
+	PEWD = 0
-	Store(0, Index(WKST,0))
+	WKST [0] = 0
-	Store(0, Index(WKST,1))
+	WKST [1] = 0
-	Store(7, UPWS)
+	UPWS = 7
 } /* End Method(\_PTS) */
 
 /*