nb/intel/sandybridge/acpi: Replace Index(a, b) with ASL 2.0 syntax

Change-Id: I75bc048d9e04be8d0cab25f6aad1c71d3e7a4008
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/71506
Reviewed-by: Felix Singer <felixsinger@posteo.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/northbridge/intel/sandybridge/acpi/hostbridge.asl

@@ -135,7 +135,7 @@ Device (MCHC)
 
 		While (Local0 < Local1) {
 			/* Store _PSS entry Control value to Local2 */
-			Local2 = DeRefOf (Index (DeRefOf (Index (\_SB.CP00._PSS, Local0)), 4)) >> 8
+			Local2 = DeRefOf (DeRefOf (\_SB.CP00._PSS[Local0])[4]) >> 8
 			If (Local2 == Arg0) {
 				Return (Local0 - 1)
 			}