On the first generation of Allwinner SoCs (A10-A31), the i2s controller was
using the MCLK as BCLK parent. However, this changed since the introduction
of the A83t and BCLK now uses the module clock as its parent.

Let's introduce a hook to get the parent rate and use that in our divider
calculations.

Fixes: 7d299381 ("ASoC: sun4i-i2s: Add support for H3")
Fixes: 21faaea1 ("ASoC: sun4i-i2s: Add support for A83T")
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://lore.kernel.org/r/0b6665be216b3bd0e7bc43724818f05f3f8ee881.1566242458.git-series.maxime.ripard@bootlin.comSigned-off-by: Mark Brown <broonie@kernel.org>