block: rkmtd: select CONFIG_RANDOM_UUID explicitly

This option is necessary to compile any way.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 048a6ca..b897cf1 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -265,6 +265,7 @@
 
 config RKMTD
 	bool "Rockchip rkmtd virtual block device"
+	select RANDOM_UUID
 	help
 	  Enable "rkmtd" class and driver to create a virtual block device
 	  to transfer Rockchip boot block data to and from NAND with block