ASoC: adau1977: remove platform data and move micbias bindings include

The change removes the platform_data include/definition. It only contains
some values for the MICBIAS.
These are moved into 'dt-bindings/sound/adi,adau1977.h' so that they can be
used inside device-trees. When moving then, they need to be converted to
pre-compiler defines, so that the DT compiler can understand them.

The driver then, also needs to include the new
'dt-bindings/sound/adi,adau1977.h' file.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20201019105313.24862-1-alexandru.ardelean@analog.com
Signed-off-by: Mark Brown <broonie@kernel.org>