ARM MPS2 timer

The MPS2 platform has simple general-purpose 32 bits timers.

Required properties:
- compatible	: Should be "arm,mps2-timer"
- reg		: Address and length of the register set
- interrupts	: Reference to the timer interrupt

Required clocking property, have to be one of:
- clocks	  : The input clock of the timer
- clock-frequency : The rate in HZ in input of the ARM MPS2 timer

Examples:

timer1: mps2-timer@40000000 {
	compatible = "arm,mps2-timer";
	reg = <0x40000000 0x1000>;
	interrupts = <8>;
	clocks = <&sysclk>;
};

timer2: mps2-timer@40001000 {
	compatible = "arm,mps2-timer";
	reg = <0x40001000 0x1000>;
	interrupts = <9>;
	clock-frequency = <25000000>;
};