src: Remove redundant use of ACPI offset(0)

IASL version 20180927 and greater, detects Unnecessary/redundant uses of
the Offset() operator within a Field Unit list.
It then sends a remark "^ Unnecessary/redundant use of Offset"

example:
    OperationRegion (OPR1, SystemMemory, 0x100, 0x100)
    Field (OPR1)
    {
        Offset (0),     // Never needed
        FLD1, 32,
        Offset (4),     // Redundant, offset is already 4 (bytes)
        FLD2, 8,
        Offset (64),    // OK use of Offset.
        FLD3, 16,
    }

We will have those remarks:
dsdt.asl     14:         Offset (0),
Remark   2158 -                 ^ Unnecessary/redundant use of Offset operator

dsdt.asl     16:         Offset (4),
Remark   2158 -                 ^ Unnecessary/redundant use of Offset operator

Change-Id: I260a79ef77025b4befbccc21f5999f89d90c1154
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43283
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-by: Jason Glenesk <jason.glenesk@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/southbridge/intel/i82801ix/acpi/ich9.asl b/src/southbridge/intel/i82801ix/acpi/ich9.asl
index 25a756e..f720505 100644
--- a/src/southbridge/intel/i82801ix/acpi/ich9.asl
+++ b/src/southbridge/intel/i82801ix/acpi/ich9.asl
@@ -32,8 +32,7 @@
 	OperationRegion(GPIO, SystemIO, DEFAULT_GPIOBASE, 0x3c)
 	Field(GPIO, ByteAcc, NoLock, Preserve)
 	{
-		Offset(0x00),	// GPIO Use Select
-		GU00, 8,
+		GU00, 8,	// GPIO Use Select
 		GU01, 8,
 		GU02, 8,
 		GU03, 8,