clk: meson: axg-audio: don't register inputs in the onecell data

Clock inputs should not be exported outside the controller. It is a hack
to have a stable global clock name within the clock controller, even for
clocks external to the controller.

There is an ongoing effort to replace this hack with something better.
The first step is to not register those clocks in the provider anymore,
so we can completely remove them later on.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lkml.kernel.org/r/20190329160649.31603-4-jbrunet@baylibre.com