ACPICA: Move all public H/W interfaces to new hwxface

Move public interfaces from hwregs.c to new file, hwxface.c -
similar to the structure of the other ACPICA components.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>