regulator: rk808: Add regulator driver for RK805

Add support for the rk805 regulator. The regulator module consists
of 4 DCDCs, 3 LDOs.

The output voltages are configurable and are meant to supply power
to the main processor and other components.

Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Signed-off-by: Joseph Chen <chenjh@rock-chips.com>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>