ACPICA: Drop acpi_set_gpe

The acpi_set_gpe() function is a little awkward, because it doesn't
really work as advertised in the "disable" case.  Namely, if a GPE
has been enabled with acpi_enable_gpe() and triggered a notification
to occur, and if acpi_set_gpe() is used to disable it before
acpi_ev_asynch_enable_gpe() runs, the GPE will be immediately enabled
by the latter as though the acpi_set_gpe() had no effect.

Thus, since it's been possible to make all of its callers use
alternative operations to disable or enable GPEs, acpi_set_gpe() can
be dropped.

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