ASoC: jz4740: Add dynamic sampling rate support to jz4740-i2s

The div clock register is not modified during jz4740_i2s_hw_params.
Hence, default sampling rates are actually used regardless of
sampling rates input from userspace.

This patch adds support to calculate the value of the divider from
the parameters passed from userspace and update the relevant div
registers

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>