ACPI / ACPICA: Simplify acpi_ev_initialize_gpe_block()

Simplify the main loop in acpi_ev_initialize_gpe_block() by
rearranging code and removing the "enabled" label that is not
necessary any more.

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