ALSA: oxygen: simplify model-specific MCLK handling

Replace the get_i2s_mclk callback with tables of MCLK values.  This
simplifies the MCLK-handling code in both the framework and the model-
specific drivers.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>