RDA Micro RDA8810PL Interrupt Controller

The interrupt controller in RDA8810PL SoC is a custom interrupt controller
which supports up to 32 interrupts.

Required properties:

- compatible: Should be "rda,8810pl-intc".
- reg: Specifies base physical address of the registers set.
- 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 2.

The interrupt sources are as follows:

ID	Name
------------
0:	PULSE_DUMMY
1:	I2C
2:	NAND_NFSC
3:	SDMMC1
4:	SDMMC2
5:	SDMMC3
6:	SPI1
7:	SPI2
8:	SPI3
9:	UART1
10:	UART2
11:	UART3
12:	GPIO1
13:	GPIO2
14:	GPIO3
15:	KEYPAD
16:	TIMER
17:	TIMEROS
18:	COMREG0
19:	COMREG1
20:	USB
21:	DMC
22:	DMA
23:	CAMERA
24:	GOUDA
25:	GPU
26:	VPU_JPG
27:	VPU_HOST
28:	VOC
29:	AUIFC0
30:	AUIFC1
31:	L2CC

Example:
		apb@20800000 {
			compatible = "simple-bus";
			...
			intc: interrupt-controller@0 {
				compatible = "rda,8810pl-intc";
				reg = <0x0 0x1000>;
				interrupt-controller;
				#interrupt-cells = <2>;
			};
		};
