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/board/firefly/firefly-rk3288/Kconfig b/board/firefly/firefly-rk3288/Kconfig
new file mode 100644
index 0000000..1c2bca8
--- /dev/null
+++ b/board/firefly/firefly-rk3288/Kconfig
@@ -0,0 +1,15 @@
+if TARGET_FIREFLY_RK3288
+
+config SYS_BOARD
+	default "firefly-rk3288"
+
+config SYS_VENDOR
+	default "firefly"
+
+config SYS_CONFIG_NAME
+	default "firefly-rk3288"
+
+config BOARD_SPECIFIC_OPTIONS # dummy
+	def_bool y
+
+endif