mb/pcengines/apu2: Convert to ASL 2.0 syntax

Change-Id: Ie2b1b27c0715fc223e644c3df6c0e9cb876322c8
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46213
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Frans Hendriks <fhendriks@eltan.com>
Reviewed-by: Michał Żygowski <michal.zygowski@3mdeb.com>

src/mainboard/pcengines/apu2/acpi/sleep.asl

@@ -30,9 +30,9 @@ Method(_PTS, 1) {
 	/* DBGO("\n") */
 
 	/* Clear wake status structure. */
-	Store(0, Index(WKST,0))
-	Store(0, Index(WKST,1))
-	Store(7, UPWS)
+	WKST [0] = 0
+	WKST [1] = 0
+	UPWS = 7
 	\_SB.APTS(Arg0)
 } /* End Method(\_PTS) */
 
@@ -58,7 +58,7 @@ Method(\_WAK, 1) {
 	/* DBGO(" to S0\n") */
 
 	/* clear USB wake up signal */
-	Store(1, USBS)
+	USBS = 1
 
 	\_SB.AWAK(Arg0)