ASoC: rockchip: Add machine driver for RK3399 GRU Boards

Because we need to support the multiple codecs (MAX98357A/RT5514/DA7219)
on the RK3399 GRU boards, this patch can help us to support these codecs.

Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>