ASoC: adau17x1: Mark DSP parameter memory as readable and precious

To be able to read back data from the DSP parameter memory the register
range needs to be marked as readable. At the same time we do not want them
to e.g. appear in debugfs output so mark them as precious as well.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>