ASoC: wm8731: Factor our MCLK and mutex initialisation

The code for initialising the MCLK and mutex is identical in the I2C and SPI
probe functions so just move this out into wm8731_init().

Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20220325153121.1598494-5-broonie@kernel.org


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