UefiCpuPkg/CpuCommonFeaturesLib: Remove XD enable/disable logic

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2329

XD (ExecutionDisable) feature, when turned on, allows page table
entry BIT63 set to 1 indicating the memory pointed by the page table
is disallowed to execute.
DxeIpl::CreateIdentityMappingPageTables() enables the XD when CPU
supports it.
Later DxeCore modifies the page table to set the BIT63 to protect
the stack/heap to disallow code execution in stack/heap.

UefiCpuPkg/CpuCommonFeaturesLib enables/disables the XD feature
according to PcdCpuFeaturesSetting.
When XD is disabled, GP fault is generated immediately because some
page entries have BIT63 set.

To fix this issue, this patch removes the XD feature logic from
UefiCpuPkg/CpuCommonFeaturesLib so the XD feature is only taken
care of by DxeIpl.

Signed-off-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>

UefiCpuPkg/Library/CpuCommonFeaturesLib/CpuCommonFeaturesLib.inf

@@ -4,7 +4,7 @@
 #  This library registers CPU features defined in Intel(R) 64 and IA-32
 #  Architectures Software Developer's Manual.
 #
-# Copyright (c) 2017 - 2018, Intel Corporation. All rights reserved.<BR>
+# Copyright (c) 2017 - 2019, Intel Corporation. All rights reserved.<BR>
 #
 #  SPDX-License-Identifier: BSD-2-Clause-Patent
 #
@@ -34,7 +34,6 @@
   C1e.c
   ClockModulation.c
   Eist.c
-  ExecuteDisable.c
   FastStrings.c
   FeatureControl.c
   LimitCpuIdMaxval.c