MdeModulePkg/DxeIpl: Introduce PCD PcdUse5LevelPageTable

MdeModulePkg/DxeIpl: Introduce PCD PcdUse5LevelPageTable

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2008

The PCD indicates if 5-Level Paging will be enabled in long mode.
5-Level Paging will not be enabled when the PCD is TRUE but CPU
doesn't support 5-Level Paging.

Signed-off-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>
Signed-off-by: Eric Dong <eric.dong@intel.com>