x86/xstate: also use alternative asm on xsave side

x86/xstate: also use alternative asm on xsave side

From: Shuai Ruan <shuai.ruan@linux.intel.com>

This patch use alternavtive asm on the xsave side.
As xsaves use modified optimization like xsaveopt, xsaves
may not writing the FPU portion of the save image too.
So xsaves also need some extra tweaks.

Signed-off-by: Shuai Ruan <shuai.ruan@linux.intel.com>
Fix XSAVES opcode. Extend the other respective XSAVEOPT conditional to
cover XSAVES as well. Re-wrap comment being adjusted.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>