UefiCpuPkg: PiSmmCpuDxeSmm skip MSR_IA32_MISC_ENABLE manipulation on AMD

UefiCpuPkg: PiSmmCpuDxeSmm skip MSR_IA32_MISC_ENABLE manipulation on AMD

AMD does not support MSR_IA32_MISC_ENABLE.  Accessing that register
causes and exception on AMD processors.  If Execution Disable is
supported, but if the processor is an AMD processor, skip manipulating
MSR_IA32_MISC_ENABLE[34] XD Disable bit.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Garrett Kirkendall <garrett.kirkendall@amd.com>
Message-Id: <20200622131825.1352-5-Garrett.Kirkendall@amd.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>