OvmfPkg/CcExitLib: Refactor TDX MmioExit

OvmfPkg/CcExitLib: Refactor TDX MmioExit

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4169

The previous TDX MmioExit doesn't handle the Mmio instructions correctly
in some scenarios. This patch refactors the implementation to fix the
issues.

Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Ryan Afranji <afranji@google.com>
Reported-by: Ryan Afranji <afranji@google.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>