MPC83xx timer devices

MPC83xx SoCs offer a decrementer interrupt that can be used to implement delay
functionality, and periodically triggered actions.

Required properties:
- compatible: must be "fsl,mpc83xx-timer"
- clocks: must be a reference to the system's CSB (coherent system bus) clock,
  provided by one of the "fsl,mpc83xx-clk" devices

Example:

socclocks: clocks {
	compatible = "fsl,mpc832x-clk";
	#clock-cells = <1>;
};

timer {
	compatible = "fsl,mpc83xx-timer";
	clocks = <&socclocks MPC83XX_CLK_CSB>;
};