IntelSiliconPkg/IntelVTdDxe: Do global invalidation before boot

IntelSiliconPkg/IntelVTdDxe: Do global invalidation before boot

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1547

V2:
Abandon V1.
Do global invalidation of context-cache and IOTLB at
ExitBootServices.

V1:
Only doing IOTLB invalidation would cause a BSOD
'DRIVER_VERIFIER_DMA_VIOLATION' while changing the second
level page entry's attributes. So always do the global
invalidation of context-cache and IOTLB.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Rangasai V Chaganty <rangasai.v.chaganty@intel.com>
Signed-off-by: Zhichao Gao <zhichao.gao@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Chasel Chiu <chasel.chiu@intel.com>