rockchip: Add basic support for firefly-rk3288

The Firefly RK3288 is a suitable target board for initial mainline Rockchip
support. It includes a good set of peripherals, a recent SoC and it is
readily available.

This adds only some basic files required to allow the baord to display a
serial message in SPL and hang.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-rockchip/rk3288/Kconfig b/arch/arm/mach-rockchip/rk3288/Kconfig
index 26d5951..7a77615 100644
--- a/arch/arm/mach-rockchip/rk3288/Kconfig
+++ b/arch/arm/mach-rockchip/rk3288/Kconfig
@@ -1,6 +1,16 @@
 if ROCKCHIP_RK3288
 
+config TARGET_FIREFLY_RK3288
+	bool "Firefly-RK3288"
+	help
+	  Firefly is a RK3288-based development board with 2 USB ports,
+	  HDMI, VGA, micro-SD card, audio, WiFi  and Gigabit Ethernet, It
+	  also includes on-board eMMC and 1GB of SDRAM. Expansion connectors
+	  provide access to display pins, I2C, SPI, UART and GPIOs.
+
 config SYS_SOC
 	default "rockchip"
 
+source "board/firefly/firefly-rk3288/Kconfig"
+
 endif