rockchip: rk3188: Add Radxa Rock board

The Rock is a RK3188 based single board computer by Radxa.
Currently it still relies on the proprietary DDR init and
cannot use the generic SPL, but at least is able to boot
a linux kernel and system up to a regular login prompt.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Simon Glass <sjg@chromium.org>
Fix sort order in defconfig, enable CONFIG_SPL_TINY_MEMSET:
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/radxa/rock/MAINTAINERS b/board/radxa/rock/MAINTAINERS
new file mode 100644
index 0000000..c5f59c0
--- /dev/null
+++ b/board/radxa/rock/MAINTAINERS
@@ -0,0 +1,6 @@
+RADXA_ROCK
+M:	Heiko Stuebner <heiko@sntech.de>
+S:	Maintained
+F:	board/radxa/rock
+F:	include/configs/rock.h
+F:	configs/rock_defconfig