XCNTXT_MASK is 'all supported xfeatures' before introducing supervisor
xstates.  Rename it to XFEATURE_MASK_USER_SUPPORTED to make clear that
these are user xstates.

Replace XFEATURE_MASK_SUPERVISOR with the following:
- XFEATURE_MASK_SUPERVISOR_SUPPORTED: Currently nothing.  ENQCMD and
  Control-flow Enforcement Technology (CET) will be introduced in separate
  series.
- XFEATURE_MASK_SUPERVISOR_UNSUPPORTED: Currently only Processor Trace.
- XFEATURE_MASK_SUPERVISOR_ALL: the combination of above.
Co-developed-by: NYu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: NFenghua Yu <fenghua.yu@intel.com>
Signed-off-by: NYu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Reviewed-by: NDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: NTony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/20200512145444.15483-3-yu-cheng.yu@intel.com