hwf-x86: use CFI statements for 'is_cpuid_available'

* src/hwf-x86.c (FORCE_FUNC_FRAME_POINTER): Remove.
(CFI_ADJUST_CFA_OFFSET, CFI_PUSH4, CFI_POP4): New.
(is_cpuid_available): Use CFI statements instead of frame-pointer
attribute.

With newer GCC, "no-omit-frame-pointer" attribute no longer
enforces frame pointer usage in function.

• Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>