ASoC: max98925: Constify regmap config and other codec data

Constify local structures (snd_soc_dai_ops, snd_soc_codec_driver,
regmap_config) and array (reg_defaults) which are not modified by the
driver and passed to core as pointer to const.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>