ACPI: EC: Don't re-enable GPE for each transaction.

With the auto selection of operation mode, absence of GPEs does not
really degrade performance, so let PM code to handle
enabling/disabling GPEs.
This is a revert of 5d57a6a5

,
which was meant to be temporary.

Reference: http://bugzilla.kernel.org/show_bug.cgi?id=7977

Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>