ARM: stv0991: 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/Kconfig b/arch/arm/Kconfig
index 0a0d19f..af2d4f4 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -235,6 +235,8 @@
 config TARGET_STV0991
 	bool "Support stv0991"
 	select CPU_V7
+	select DM
+	select DM_SERIAL
 
 config TARGET_X600
 	bool "Support x600"
diff --git a/configs/stv0991_defconfig b/configs/stv0991_defconfig
index e8cf311..1884ac4 100644
--- a/configs/stv0991_defconfig
+++ b/configs/stv0991_defconfig
@@ -2,5 +2,3 @@
 CONFIG_ARM=y
 CONFIG_TARGET_STV0991=y
 CONFIG_SYS_MALLOC_F_LEN=0x2000
-CONFIG_DM=y
-CONFIG_DM_SERIAL=y