[ALSA] oxygen: reduce SPI clock frequency for AK4396/WM8785

[ALSA] oxygen: reduce SPI clock frequency for AK4396/WM8785

According to the datasheets, the SPI clock cycle must be at least 200 ns
for the AK4396 and the WM8785, so we cannot use the default 160 ns.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>