ARM: rmobile: use "select" instead of default value in defconfig

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/cpu/armv7/rmobile/Kconfig b/arch/arm/cpu/armv7/rmobile/Kconfig
index 2b333a3..57dccec 100644
--- a/arch/arm/cpu/armv7/rmobile/Kconfig
+++ b/arch/arm/cpu/armv7/rmobile/Kconfig
@@ -8,24 +8,36 @@
 
 config TARGET_GOSE
 	bool "Gose board"
+	select DM
+	select DM_SERIAL
 
 config TARGET_KOELSCH
 	bool "Koelsch board"
+	select DM
+	select DM_SERIAL
 
 config TARGET_LAGER
 	bool "Lager board"
+	select DM
+	select DM_SERIAL
 
 config TARGET_KZM9G
 	bool "KZM9D board"
 
 config TARGET_ALT
 	bool "Alt board"
+	select DM
+	select DM_SERIAL
 
 config TARGET_SILK
 	bool "Silk board"
+	select DM
+	select DM_SERIAL
 
 config TARGET_PORTER
 	bool "Porter board"
+	select DM
+	select DM_SERIAL
 
 endchoice