rockchip: add usb mass storage feature support for rk3288

Enable ums feature for rk3288 boards, so that we can mount the mmc
device to PC.
Signed-off-by: NZiyuan Xu <xzy.xu@rock-chips.com>
Acked-by: NSimon Glass <sjg@chromium.org>

include/configs/rk3288_common.h

@@ -96,6 +96,10 @@
 #define CONFIG_FASTBOOT_BUF_ADDR	CONFIG_SYS_LOAD_ADDR
 #define CONFIG_FASTBOOT_BUF_SIZE	0x08000000
 
+/* usb mass storage */
+#define CONFIG_USB_FUNCTION_MASS_STORAGE
+#define CONFIG_CMD_USB_MASS_STORAGE
+
 #define CONFIG_USB_GADGET_DOWNLOAD
 #define CONFIG_G_DNL_MANUFACTURER	"Rockchip"
 #define CONFIG_G_DNL_VENDOR_NUM		0x2207