ACPICA: Events: Cleanup of resetting the GPE handler to NULL before removing

ACPICA commit b2b18bb38045404e253f10787b8a4ae6e94cdee6

This patch prevents acpi_remove_gpe_handler() from leaking the stale
gpe_event_info->Dispatch.Handler to the caller to avoid possible NULL pointer
references. Lv Zheng.

Link: https://github.com/acpica/acpica/commit/b2b18bb3


Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>