ASoC: codecs: wcd938x: fix soundwire initialisation race

ASoC: codecs: wcd938x: fix soundwire initialisation race

Make sure that the soundwire device used for register accesses has been
enumerated and initialised before trying to read the codec variant
during component probe.

This specifically avoids interpreting (a masked and shifted) -EBUSY
errno as the variant:

	wcd938x_codec audio-codec: ASoC: error at soc_component_read_no_lock on audio-codec for register: [0x000034b0] -16

in case the soundwire device has not yet been initialised, which in turn
prevents some headphone controls from being registered.

Fixes: 8d78602aa87a ("ASoC: codecs: wcd938x: add basic driver")
Cc: stable@vger.kernel.org	# 5.14
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Reported-by: Steev Klimaszewski <steev@kali.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Tested-by: Steev Klimaszewski <steev@kali.org>
Link: https://lore.kernel.org/r/20230701094723.29379-1-johan+linaro@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>