x86/xsaves: Define macros for xsave instructions

Define macros for xsave, xsaveopt, xsaves, xrstor, and xrstors inline
instructions. The instructions will be used for saving and restoring xstate.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1401387164-43416-7-git-send-email-fenghua.yu@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>