Add support to allow host to redefine individual OSL prototypes.

This change enables the host to redefine OSL prototypes found in the
acpiosxf.h file. This allows the host to implement OSL interfaces with
a macro or inlined function. Further, it allows the host to add any
additional required modifiers such as __iomem, __init, __exit, etc.,
as necessary on a per-interface basis. Enables maximum flexibility
for the OSL interfaces. Lv Zheng.