x86/xsaves: Save xstate to task's xsave area in __save_fpu during booting time

x86/xsaves: Save xstate to task's xsave area in __save_fpu during booting time

__save_fpu() can be called during early booting time when cpu caps are not
enabled and alternative can not be used yet. Therefore, it calls
xsave_state_booting() during booting time to save xstate to task's xsave area.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1401387164-43416-14-git-send-email-fenghua.yu@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>