IntelSiliconPkg/VTdDxe: return unsupported for exceptionlist

Since the exception list is not a recommended way, we returns
EFI_UNSUPPORTED in the sample code.

Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
(cherry picked from commit e5d847476a)

IntelSiliconPkg/Feature/VTd/PlatformVTdSampleDxe/PlatformVTdSampleDxe.c

@@ -359,6 +359,7 @@ PlatformVTdGetExceptionDeviceList (
   // Uncomment to take affect and comment the sample codes for device scope
   // based exception list.
   //
+  /*
   *DeviceInfo = AllocateZeroPool (sizeof(mExceptionPciDeviceIdList));
   if (*DeviceInfo == NULL) {
     return EFI_OUT_OF_RESOURCES;
@@ -366,8 +367,8 @@ PlatformVTdGetExceptionDeviceList (
   CopyMem (*DeviceInfo, mExceptionPciDeviceIdList, sizeof(mExceptionPciDeviceIdList));
 
   *DeviceInfoCount = ARRAY_SIZE(mExceptionPciDeviceIdList);
-
-  return EFI_SUCCESS;
+  */
+  return EFI_UNSUPPORTED;
 }
 
 EDKII_PLATFORM_VTD_POLICY_PROTOCOL  mPlatformVTdSample = {