drivers/intel/gma/acpi: Use ASL 2.0 syntax to access arrays

Replace Index(FOO, 1337) with FOO[1337].

Change-Id: I534c1581e587908feeb06fd7725c5895649dcfb1
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60456
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
diff --git a/src/drivers/intel/gma/acpi/common.asl b/src/drivers/intel/gma/acpi/common.asl
index 79960e1..254a66d 100644
--- a/src/drivers/intel/gma/acpi/common.asl
+++ b/src/drivers/intel/gma/acpi/common.asl
@@ -42,7 +42,7 @@
 			{
 				Decrement (Local0)
 			}
-			XBCM (DerefOf (Index (BRIG, Local0)))
+			XBCM (DerefOf (BRIG[Local0]))
 		}
 	}
 
@@ -60,6 +60,6 @@
 			{
 				Increment (Local0)
 			}
-			XBCM (DerefOf (Index (BRIG, Local0)))
+			XBCM (DerefOf (BRIG[Local0]))
 		}
 	}