x86, AVX-512: Enable AVX-512 States Context Switch

This patch enables Opmask, ZMM_Hi256, and Hi16_ZMM AVX-512 states for
xstate context switch.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1392931491-33237-2-git-send-email-fenghua.yu@intel.com


Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: <stable@vger.kernel.org> # hw enabling