ACPI: implement Generic Event Device

Generic Event Device described in ACPI 6.1 allows platforms to handle
platform interrupts in ACPI ASL statements. It borrows constructs like
_EVT from GPIO events. All interrupts are listed in _CRS and the handler
is written in _EVT method. Here is an example.

Device (GED0)
{

	Name (_HID, "ACPI0013")
	Name (_UID, 0)
	Name(_CRS, ResourceTemplate ()
	{
		Interrupt(ResourceConsumer, Edge, ActiveHigh, Shared, , , )
		 {123}
	})

	Method (_EVT, 1) {
		if (Lequal(123, Arg0))
		{
		}
	}
}

Wake capability has not been implemented yet.

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>