KVM: x86: Enable Intel AVX-512 for guest

Expose Intel AVX-512 feature bits to guest. Also add checks for
xcr0 AVX512 related bits according to spec:
http://download-software.intel.com/sites/default/files/managed/71/2e/319433-017.pdf

Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --cc arch/x86/include/asm/xsave.h
Simple merge

diff --cc arch/x86/kvm/cpuid.c
Simple merge

diff --cc arch/x86/kvm/x86.c
Simple merge

diff --cc arch/x86/kvm/x86.h
Simple merge