clk: meson: axg_audio: replace prefix axg by aud

The audio clock controller is compatible with axg and g12a SoC family.
Having each clock name prefixed with "axg_" looks weird on the g12a.
This change replace the "axg_" by "aud_" in fron the clock names.
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lkml.kernel.org/r/20190329160649.31603-3-jbrunet@baylibre.com