ACPICA: Return u32 from acpi_dispatch_gpe()

In some cases it is useful to know whether or not the
acpi_ev_detect_gpe() called by acpi_dispatch_gpe() has found
the GPE to be active, so return the return value of it (whose
data type is u32) from latter.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>