mb/asus/a88xm-e: Convert to ASL 2.0 syntax

Generated 'build/dsdt.dsl' files are identical.

Change-Id: I8887b869e9ed809f7861b810c2fb994fa2ee062e
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46156
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>

src/mainboard/asus/a88xm-e/acpi/sleep.asl

@@ -22,10 +22,10 @@ Name(WKST,Package(){Zero, Zero})
 Method(\_PTS, 1) {
 
 	/* Clear wake status structure. */
-	Store(0, Index(WKST,0))
-	Store(0, Index(WKST,1))
+	WKST [0] = 0
+	WKST [1] = 0
 
-	Store (0x07, UPWS)
+	UPWS = 0x07
 } /* End Method(\_PTS) */
 
 /*