ASoC: max98925: Remove control_data initialization

The control_data field of the snd_soc_codec struct is no longer used by
ASoC drivers using standard regmap IO.

There is no need to initialize the field to point to the drivers regmap
struct, so drop that.

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