OvmfPkg/Sec: Enable cache early to speed up booting

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198



Currently, the OVMF code relies on the hypervisor to enable the cache
support on the processor in order to improve the boot speed. However,
with SEV-ES, the hypervisor is not allowed to change the CR0 register
to enable caching.

Update the OVMF Sec support to enable caching in order to improve the
boot speed when running as an SEV-ES guest.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>