ASoC: qcom: apq8016_sbc: Allow routing audio through QDSP6

Merge series from Stephan Gerhold <stephan@gerhold.net>:

This series makes it possible to route audio through the combined
audio/modem DSP on MSM8916/APQ8016 devices instead of bypassing it using
the LPASS drivers. This is necessary to support certain functionality such
as voice call audio. See PATCH 4/5 for details.

Also, qcom,apq8016-sbc.txt is converted to DT schema by adding it to the
existing qcom,sm8250.yaml. The bindings are similar enough that it is easier
to share a single schema instead of duplicating everything into multiple ones.