ASoC: add driver for Rockchip RK3xxx I2S controller

Add driver for i2s controller found on rk3066, rk3168 and rk3288
processors from rockchip.

Tested on the RK3288 SDK board.

Signed-off-by: Jianqun Xu <xjq@rock-chips.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/sound/soc/Makefile b/sound/soc/Makefile
index 5f1df02..534714a 100644
--- a/sound/soc/Makefile
+++ b/sound/soc/Makefile
@@ -24,6 +24,7 @@
 obj-$(CONFIG_SND_SOC)	+= omap/
 obj-$(CONFIG_SND_SOC)	+= kirkwood/
 obj-$(CONFIG_SND_SOC)	+= pxa/
+obj-$(CONFIG_SND_SOC)	+= rockchip/
 obj-$(CONFIG_SND_SOC)	+= samsung/
 obj-$(CONFIG_SND_SOC)	+= s6000/
 obj-$(CONFIG_SND_SOC)	+= sh/