Device Tree Clock bindings for arch-vt8500

This binding uses the common clock binding[1].

[1] Documentation/devicetree/bindings/clock/clock-bindings.txt

Required properties:
- compatible : shall be one of the following:
	"via,vt8500-pll-clock" - for a VT8500/WM8505 PLL clock
	"wm,wm8650-pll-clock" - for a WM8650 PLL clock
	"wm,wm8750-pll-clock" - for a WM8750 PLL clock
	"wm,wm8850-pll-clock" - for a WM8850 PLL clock
	"via,vt8500-device-clock" - for a VT/WM device clock

Required properties for PLL clocks:
- reg : shall be the control register offset from PMC base for the pll clock.
- clocks : shall be the input parent clock phandle for the clock. This should
	be the reference clock.
- #clock-cells : from common clock binding; shall be set to 0.

Required properties for device clocks:
- clocks : shall be the input parent clock phandle for the clock. This should
	be a pll output.
- #clock-cells : from common clock binding; shall be set to 0.


Device Clocks

Device clocks are required to have one or both of the following sets of
properties:


Gated device clocks:

Required properties:
- enable-reg : shall be the register offset from PMC base for the enable
	register.
- enable-bit : shall be the bit within enable-reg to enable/disable the clock.


Divisor device clocks:

Required property:
- divisor-reg : shall be the register offset from PMC base for the divisor
	register.
Optional property:
- divisor-mask : shall be the mask for the divisor register. Defaults to 0x1f
	if not specified.


For example:

ref25: ref25M {
	#clock-cells = <0>;
	compatible = "fixed-clock";
	clock-frequency = <25000000>;
};

plla: plla {
	#clock-cells = <0>;
	compatible = "wm,wm8650-pll-clock";
	clocks = <&ref25>;
	reg = <0x200>;
};

sdhc: sdhc {
	#clock-cells = <0>;
	compatible = "via,vt8500-device-clock";
	clocks = <&pllb>;
	divisor-reg = <0x328>;
	divisor-mask = <0x3f>;
	enable-reg = <0x254>;
	enable-bit = <18>;
};