x86: xsaveopt kernel enabling patches - v2

AVX Programming Reference (June, 2010 version) located at
http://software.intel.com/en-us/avx/ refers to the optimized
extended state save instruction "xsaveopt".

xsaveopt is similar to xsave and incorporates optimizations specifically
targeted for speeding up context switch save, like:
a. if a state is in an INIT state, the instruction may clear the corresponding
   bit in the xheader.bv with out writing the actual state in to the memory.
b. if the state hasn't been modified since the last xrstor, the instruction
   may not write out the state to the save area.

Following patches enable the use of xsaveopt for context switch save/restore
of the extended state.

changes in v2:
Split the cpu feature detection bits in to multiple patches along with the
misc changes in the init_scattered_cpuid_features() -- Requested by hpa.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>

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