x86/xsaves: Clean up code in xstate offsets computation in xsave area

x86/xsaves: Clean up code in xstate offsets computation in xsave area

This patch cleans up some code in xstate offsets computation in xsave
area:

1. It changes xstate_comp_offsets as an array. This avoids possible NULL pointer
   caused by possible kmalloc() failure during boot time.
2. It changes the global variable xstate_comp_sizes to a local variable because
   it is used only in setup_xstate_comp().
3. It adds missing offsets for FP and SSE in xsave area.

Signed-off-by: Fenghua Yu <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: H. Peter Anvin <[email protected]>