reset: Add support for the Amlogic Meson SoC Reset Controller

This patch adds the platform driver for the Amlogic Meson SoC Reset
Controller.

The Meson8b and GXBB SoCs are supported.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>