rockchip: block: add rkmtd class and drivers

Add rkmtd class and drivers to create a virtual block device
to transfer Rockchip boot block data to and from NAND with
block orientated tools like "ums" and "rockusb".

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 1abea3f..048a6ca 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -262,3 +262,10 @@
 	help
 	  Make the block subsystem use 64bit sector addresses, rather than the
 	  default of 32bit.
+
+config RKMTD
+	bool "Rockchip rkmtd virtual block device"
+	help
+	  Enable "rkmtd" class and driver to create a virtual block device
+	  to transfer Rockchip boot block data to and from NAND with block
+	  orientate tools like "ums" and "rockusb".