Affects PM1 Control register only. When reading the register, zero
the write-only bits as per the ACPI spec.  ACPICA BZ 443. Lin Ming.

http://www.acpica.org/bugzilla/show_bug.cgi?id=443Signed-off-by: NLin Ming <ming.m.lin@intel.com>
Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLen Brown <len.brown@intel.com>