rockchip: Add SPI driver

Add a SPI 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/spi/Makefile b/drivers/spi/Makefile
index ee88aa1..de241be 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -39,6 +39,7 @@
 obj-$(CONFIG_MXC_SPI) += mxc_spi.o
 obj-$(CONFIG_MXS_SPI) += mxs_spi.o
 obj-$(CONFIG_OMAP3_SPI) += omap3_spi.o
+obj-$(CONFIG_ROCKCHIP_SPI) += rk_spi.o
 obj-$(CONFIG_SANDBOX_SPI) += sandbox_spi.o
 obj-$(CONFIG_SH_SPI) += sh_spi.o
 obj-$(CONFIG_SH_QSPI) += sh_qspi.o