ASoC: loongson: Add I2S controller driver as platform device

The Loongson I2S controller exists not only in PCI form (LS7A bridge
chip), but also in platform device form (Loongson-2K1000 SoC).

This patch adds support for platform device I2S controller.

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Link: https://patch.msgid.link/36c143358c7f48bc2e73c30e1d2009b2f2fc6498.1728459624.git.zhoubinbin@loongson.cn


Signed-off-by: Mark Brown <broonie@kernel.org>