riscv: kconfig: Select DM and OF_CONTROL

RISC-V is a pretty new architecture and should support DM and
OF_CONTROL by default.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
diff --git a/arch/Kconfig b/arch/Kconfig
index 49f0d44..694258c 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -62,6 +62,9 @@
 config RISCV
 	bool "RISC-V architecture"
 	select SUPPORT_OF_CONTROL
+	select OF_CONTROL
+	select DM
+	imply CMD_DM
 
 config SANDBOX
 	bool "Sandbox"