irqchip: or1k-pic: Migrate from arch/openrisc/

In addition to consolidating the or1k-pic with other interrupt
controllers, this makes OpenRISC less tied to its on-cpu
interrupt controller.

All or1k-pic specific parts are moved out of irq.c and into
drivers/irqchip/irq-or1k-pic.c

In that transition, the functionality have been divided into
three chip variants.
One that handles level triggered interrupts, one that handles edge
triggered interrupts and one that handles the interrupt
controller that is present in the or1200 OpenRISC cpu
implementation.

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Link: https://lkml.kernel.org/r/1401136302-27654-1-git-send-email-stefan.kristiansson@saunalahti.fi
Acked-by: Jonas Bonn <jonas@southpole.se>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

Documentation/devicetree/bindings/interrupt-controller/opencores,or1k-pic.txt

@@ -0,0 +1,23 @@
+OpenRISC 1000 Programmable Interrupt Controller
+
+Required properties:
+
+- compatible : should be "opencores,or1k-pic-level" for variants with
+  level triggered interrupt lines, "opencores,or1k-pic-edge" for variants with
+  edge triggered interrupt lines or "opencores,or1200-pic" for machines
+  with the non-spec compliant or1200 type implementation.
+
+  "opencores,or1k-pic" is also provided as an alias to "opencores,or1200-pic",
+  but this is only for backwards compatibility.
+
+- interrupt-controller : Identifies the node as an interrupt controller
+- #interrupt-cells : Specifies the number of cells needed to encode an
+  interrupt source. The value shall be 1.
+
+Example:
+
+intc: interrupt-controller {
+	compatible = "opencores,or1k-pic-level";
+	interrupt-controller;
+	#interrupt-cells = <1>;
+};