ASoC: sun4i-i2s: Add support for DSP formats

In addition to the I2S format, the controller also supports the DSP_*
formats.

This requires some extra care on the LRCK period calculation, since the
controller, with the PCM formats, require that the value set is no longer
the periods of LRCK for a single channel, but for all of them.

Let's add the code to deal with this, and support the DSP_A and DSP_B
formats.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://lore.kernel.org/r/5562db1ac8759f12b1b87c3258223eed629ef771.1566392800.git-series.maxime.ripard@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>