Berlin PWM controller

Required properties:
- compatible: should be "marvell,berlin-pwm"
- reg: physical base address and length of the controller's registers
- clocks: phandle to the input clock
- #pwm-cells: should be 3. See pwm.txt in this directory for a description of
  the cells format.

Example:

pwm: pwm@f7f20000 {
	compatible = "marvell,berlin-pwm";
	reg = <0xf7f20000 0x40>;
	clocks = <&chip_clk CLKID_CFG>;
	#pwm-cells = <3>;
}

Add Berlin PWM controller DT binding
pwm: Add Berlin PWM controller DT binding

Add DT binding documentation for the Berlin PWM controller.

Signed-off-by: Antoine Tenart <7fc24f17b07747ca12864f96f551beca43e4577d@free-electrons.com>
Acked-by: Sebastian Hesselbarth <1d402fe89ace836b52164ed4c0f247cb6f80efc1@gmail.com>
Signed-off-by: Thierry Reding <b75a4d02013b0e68ae2c6bb0dcfd4b7bec282dc9@gmail.com>
