ACPI / EC: Do not use acpi_set_gpe

The EC driver is the last user of acpi_set_gpe() and since it is
guaranteed that the EC GPE will not be shared, acpi_disable_gpe()
and acpi_enable_gpe() may be used for disabling the GPE temporarilty
if a GPE storm is detected and re-enabling it during EC transactions.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>