arm64: dts: qcom: msm8998-xperia: Add audio clock and its pin

All smartphones of this platform are equipped with a WCD9335 audio
codec, getting its MCLK from PM8998 gpio13: add this clock to DT.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210909123733.367248-7-angelogioacchino.delregno@somainline.org