dt-bindings: clk: axg-audio: add g12a support

Add a new compatible string and additional clock ids for audio clock
controller of the g12a SoC family.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lkml.kernel.org/r/20190329160649.31603-2-jbrunet@baylibre.com