When using the legacy filter function channel requests we currently pass
the audio specific struct snd_dmaengine_dai_dma_data which isn't likely to
be helpful for actual filtering. Since there's already a field in the
structure called filter_data clearly intended for use here convert the
driver to use that.

All existing users of plain filter functions have been converted to use
an explicit compat function to override this behaviour except i.MX which
is working around this issue in its filter function and is updated to
just use filter_data directly here.
Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>