ASoC: SOF: imx: merge imx8 and imx8m drivers

ASoC: SOF: imx: merge imx8 and imx8m drivers

Now that the common interface for imx chip has been introduced,
there's no longer a need to have a separate platform driver for
imx8m. As such, merge the driver with the imx8 driver. Furthermore,
delete the old driver as it's no longer useful.

Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20250207162246.3104-6-laurentiumihalcea111@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>