x86, xsave: Track the offset, size of state in the xsave layout

Subleaves of the cpuid vector 0xd provides the offset and size of different
feature state that are managed by the xsave/xrstor. Track this for the upcoming
usage during signal handling.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <20100719230205.262987929@sbs-t61.sc.intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>