ASoC: wm8960: Read initial MCLK rate from clock API

When we have a MCLK provided by the clock API read the rate at startup
and store it so that there's something set before the machine driver has
done clocking configuration (eg, if it only configures clocking based on
sample rate).

Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230731-asoc-wm8960-clk-v1-1-69f9ffa2b10a@kernel.org


Signed-off-by: Mark Brown <broonie@kernel.org>