ARM: meson: add reset controller

Modules and submodules within Meson6 and Meson8 SoCs can be disabled by
shutting off the clock. The control for these clocks comes from several
registers that are mapped contiguously except a special register that
controls peripherals in the AO (Always-On) power domain. The reset
controller manages both the cases according to the reset ID.

Signed-off-by: Carlo Caione <carlo@caione.org>
ARM: meson: enable reset controller in kconfig

Modify the arch Kconfig to enable the reset controller

Signed-off-by: Carlo Caione <carlo@caione.org>
ARM: meson: add documentation for reset/clock controller

Add documentation for the reset and clock controller

Signed-off-by: Carlo Caione <carlo@caione.org>
ARM: meson: DTS: Add clock controller binding

Signed-off-by: Carlo Caione <carlo@caione.org>
ARM: meson: DTS: Add reset controller

Signed-off-by: Carlo Caione <carlo@caione.org>