x86: Support XFD and AMX xsave data migration

XFD(eXtended Feature Disable) allows to enable a
feature on xsave state while preventing specific
user threads from using the feature.

Support save and restore XFD MSRs if CPUID.D.1.EAX[4]
enumerate to be valid. Likewise migrate the MSRs and
related xsave state necessarily.

Signed-off-by: Zeng Guang <guang.zeng@intel.com>
Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Message-Id: <20220217060434.52460-8-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>