ACPICA: Distill multiple sleep method functions to a single function

Adds acpi_hw_execute_sleep_method to handle the various sleep methods
such as _GTS, _BFS, _WAK, and _SST. Removes the specialized
functions previously used for each of these methods.

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>