clk: meson: Add GXBB AO Clock and Reset controller driver

Adds a Clock and Reset controller driver for the Always-On part
of the Amlogic Meson GXBB SoC.

It exports paired Clocks and Resets lines that will be used by
peripherals in the Always-On subsystem.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>