dt-bindings: remoteproc: Add the documentation for Meson AO ARC rproc

Amlogic Meson6, Meson8, Meson8b and Meson8m2 SoCs embed an ARC EM4
controller for always-on operations, typically used for managing system
suspend.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20210921192557.1610709-2-martin.blumenstingl@googlemail.com


Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>