Use acpi_enable_event(), acpi_disable_event(), and acpi_clear_event()
instead of writing the register directly.

This patch may be used under either the GPL v2 or the BSD-style license
used for the Intel ACPICA.
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
CC: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>