ACPI: Fix IASL Warning about unused method for GBUF check

According to the ACPI Spec for CondRefOf, the result argument is
optional.  In all of these locations, it was getting set but not
used, creating a warning in new versions of IASL.  Since it's
an optional argument, just remove it.

dsdt.aml 640:              If (CondRefOf (^GBUF, Local0)) {
Warning  3144 - Method Local is set but never used ^  (Local0)

Change-Id: Ie2f46808e92c309a63ba7661bcbd77402a08366a
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/12694
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/soc/intel/baytrail/acpi/lpe.asl

@@ -68,7 +68,7 @@ Device (LPEA)
 		Store (\LPFW, BAS2)
 
 		/* Append any Mainboard defined GPIOs */
-		If (CondRefOf (^GBUF, Local0)) {
+		If (CondRefOf (^GBUF)) {
 			ConcatenateResTemplate (^RBUF, ^GBUF, Local1)
 			Return (Local1)
 		}

src/soc/intel/braswell/acpi/lpe.asl

@@ -68,7 +68,7 @@ Device (LPEA)
 		Store (\LPFW, BAS2)
 
 		/* Append any Mainboard defined GPIOs */
-		If (CondRefOf (^GBUF, Local0)) {
+		If (CondRefOf (^GBUF)) {
 			ConcatenateResTemplate (^RBUF, ^GBUF, Local1)
 			Return (Local1)
 		}