ASoC: atmel: Fix the 8K sample parameter in I2SC master

The 8K sample parameter of 12.288Mhz main system bus clock doesn't work
because the I2SC_MR.IMCKDIV must not be 0 according to the sama5d2
series datasheet(I2SC Mode Register of Register Summary).

So use the 6.144Mhz instead of 12.288Mhz to support 8K sample.

Signed-off-by: Guiting Shen <aarongt.shen@gmail.com>
Link: https://lore.kernel.org/r/20230715030620.62328-1-aarongt.shen@gmail.com


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