ASoC: jz4740-i2s: Add local dev variable in probe function

Make the code cleaner by using a "struct device *dev" variable instead
of dereferencing it everytime from within the struct platform_device.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20200306222931.39664-3-paul@crapouillou.net


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