ASoC: codecs: wcd9335: drop unused gain hack remnant

ASoC: codecs: wcd9335: drop unused gain hack remnant

The vendor driver appears to be modifying the gain settings behind the
back of user space but these hacks never made it upstream except for
some essentially dead code that adds a constant zero to the current gain
setting on DAPM events.

Note that the volume registers still need to be written after enabling
clocks in order for any prior updates to take effect.

Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://msgid.link/r/20240119112420.7446-5-johan+linaro@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>