* Synopsys DesignWare ABP UART

Required properties:
- compatible : "snps,dw-apb-uart"
- reg : offset and length of the register set for the device.
- interrupts : should contain uart interrupt.

Clock handling:
The clock rate of the input clock needs to be supplied by one of
- clock-frequency : the input clock frequency for the UART.
- clocks : phandle to the input clock

The supplying peripheral clock can also be handled, needing a second property
- clock-names: tuple listing input clock names.
	Required elements: "baudclk", "apb_pclk"

Optional properties:
- resets : phandle to the parent reset controller.
- reg-shift : quantity to shift the register offsets by.  If this property is
  not present then the register offsets are not shifted.
- reg-io-width : the size (in bytes) of the IO accesses that should be
  performed on the device.  If this property is not present then single byte
  accesses are used.

Example:

	uart@80230000 {
		compatible = "snps,dw-apb-uart";
		reg = <0x80230000 0x100>;
		clock-frequency = <3686400>;
		interrupts = <10>;
		reg-shift = <2>;
		reg-io-width = <4>;
	};

Example with one clock:

	uart@80230000 {
		compatible = "snps,dw-apb-uart";
		reg = <0x80230000 0x100>;
		clocks = <&baudclk>;
		interrupts = <10>;
		reg-shift = <2>;
		reg-io-width = <4>;
	};

Example with two clocks:

	uart@80230000 {
		compatible = "snps,dw-apb-uart";
		reg = <0x80230000 0x100>;
		clocks = <&baudclk>, <&apb_pclk>;
		clock-names = "baudclk", "apb_pclk";
		interrupts = <10>;
		reg-shift = <2>;
		reg-io-width = <4>;
	};
