clk: meson: axg-audio: add g12a support

The g12a audio clock controller is largely similar to the existing axg
controller, with the addition of the spdif output B and TDM pad clocks.

This commit extends the existing axg audio clock controller driver
to work with multiple compatibles and add the g12a specific clocks

Signed-off-by: Maxime Jourdan <mjourdan@baylibre.com>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lkml.kernel.org/r/20190329160649.31603-5-jbrunet@baylibre.com