ASoC: jz4740-i2s: Add support for the JZ4760

The change of offset for the {rx,tx}_threshold fields in the conf
register predates the JZ4780, and was first introduced in the JZ4760.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20200306222931.39664-5-paul@crapouillou.net


Signed-off-by: Mark Brown <broonie@kernel.org>