ASoC: meson: aiu: introduce a struct for platform specific information

Introduce a struct aiu_platform_data to make the driver aware of
platform specific information. Convert the existing check for the
internal stereo audio codec (only available on GXL) to this new struct.
Support for the 32-bit SoCs will need this as well because the
AIU_CLK_CTRL_MORE register doesn't have the I2S divider bits (and we
need to use the I2S divider from AIU_CLK_CTRL instead).

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://lore.kernel.org/r/20200220205711.77953-3-martin.blumenstingl@googlemail.com
Signed-off-by: Mark Brown <broonie@kernel.org>