ACPICA: OSL: Add section to collect the divergence in acpixf.h.

This patch re-orders the interface prototypes defined in acpixf.h, moving
those having not back ported to ACPICA into a seperate section to reduce
the source code differences between Linux and ACPICA.

This can help to reduce the cost of linuxizing the follow up commits.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>