ASoC: qcom: lpass-cpu: Use optional clk APIs

ASoC: qcom: lpass-cpu: Use optional clk APIs

This driver spits out a warning for me at boot:

 sc7180-lpass-cpu 62f00000.lpass: asoc_qcom_lpass_cpu_platform_probe() error getting optional null: -2

but it looks like it is all an optional clk. Use the optional clk APIs
here so that we don't see this message and everything else is the same.

Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Banajit Goswami <bgoswami@codeaurora.org>
Fixes: ef831390c449 ("ASoC: qcom: make osr clock optional")
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20210520014807.3749797-1-swboyd@chromium.org
Signed-off-by: Mark Brown <broonie@kernel.org>