ASoC: xilinx: xlnx_i2s: Handle sysclk setting

ASoC: xilinx: xlnx_i2s: Handle sysclk setting

This driver previously only handled the set_clkdiv divider callback when
setting the SCLK Out Divider field in the I2S Timing Control register.
However, when using the simple-audio-card driver, the set_sysclk function
is called but not set_clkdiv. This caused the divider not to be set,
leaving it at an invalid value of 0 and resulting in a very low SCLK
output rate.

Handle set_clkdiv and store the sysclk (MCLK) value for later use in
hw_params to set the SCLK Out Divider such that:
MCLK/SCLK = divider * 2

Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Link: https://lore.kernel.org/r/20220120195832.1742271-4-robert.hancock@calian.com
Signed-off-by: Mark Brown <broonie@kernel.org>