rockchip: Add I2C driver

Add an I2C driver for the Rockchip RK3288, using driver model. It should work
for other Rockchip SoCs also.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index 9b45248..8ce294b 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -31,6 +31,7 @@
 obj-$(CONFIG_SYS_I2C_OMAP34XX) += omap24xx_i2c.o
 obj-$(CONFIG_SYS_I2C_PPC4XX) += ppc4xx_i2c.o
 obj-$(CONFIG_SYS_I2C_RCAR) += rcar_i2c.o
+obj-$(CONFIG_SYS_I2C_ROCKCHIP) += rk_i2c.o
 obj-$(CONFIG_SYS_I2C_S3C24X0) += s3c24x0_i2c.o
 obj-$(CONFIG_SYS_I2C_SANDBOX) += sandbox_i2c.o i2c-emul-uclass.o
 obj-$(CONFIG_SYS_I2C_SH) += sh_i2c.o