Mediatek PMIC Clock Buffer

Required properties:
- compatible: must be set to "mediatek,pmic_clock_buffer"
- mediatek,clkbuf-quantity: specify the quantity of clkbuf
- mediatek,clkbuf-config: the config of clkbuf type
	- 0: disable
	- 1: software control mode
	- 2: hardware control mode
- mediatek,clkbuf-driving-current: the driving current of clkbuf
	- 0: 0.4mA (loading: <10pF)
	- 1: 0.9mA (loading: 10~20pF, if PCB meet constraint)
	- 2: 1.4mA (loading: 20~30pF, default)
	- 3: 1.9mA (loading: >30pF)

Example:
	pmic_clock_buffer {
		compatible = "mediatek,pmic_clock_buffer";
		mediatek,clkbuf-quantity = <4>;
		mediatek,clkbuf-config = <2 1 1 2>;
		mediatek,clkbuf-driving-current = <2 2 2 2>;
	};

