clk: meson: axg: round audio system master clocks down

clk: meson: axg: round audio system master clocks down

Some of the master clocks provided by the axg audio clock controller are
system clock (spdifin and pdm sysclk). They are used to clock an internal
DSP of the related devices. Having them constantly rounded down instead
of closest is preferable.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>