UefiCpuPkg/MpInitLib: Enable 5-level paging for AP when BSP's enabled

UefiCpuPkg/MpInitLib: Enable 5-level paging for AP when BSP's enabled

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

MpInitLib is the library that's responsible to wake up APs to provide
MP PPI and Protocol services.

The patch synchronizes BSP's CR4.LA57 to each AP's CR4.LA57.
Without this change, AP may enter to GP fault when BSP's 5-level page
table is set to AP during AP wakes up.

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>
Signed-off-by: Eric Dong <eric.dong@intel.com>