Nuvoton NPCM7xx timer

Nuvoton NPCM7xx have three timer modules, each timer module provides five 24-bit
timer counters.

Required properties:
- compatible      : "nuvoton,npcm750-timer" for Poleg NPCM750.
- reg             : Offset and length of the register set for the device.
- interrupts      : Contain the timer interrupt with flags for
                    falling edge.
- clocks          : phandle of timer reference clock (usually a 25 MHz clock).

Example:

timer@f0008000 {
    compatible = "nuvoton,npcm750-timer";
    interrupts = <GIC_SPI 32 IRQ_TYPE_LEVEL_HIGH>;
    reg = <0xf0008000 0x50>;
    clocks = <&clk NPCM7XX_CLK_TIMER>;
};