ARM: uniphier: move CONFIG_SPL_* to defconfig or select

As I repeated in the ML, I am unhappy with config entries with bare
defaults.  Kick them out of arch/arm/mach-uniphier/Kconfig.

Currently, CONFIG_SPL_SERIAL_SUPPORT is not user-configurable
(build fails without it), but it should be fixed later anyway,
so I am moving CONFIG_SPL_SERIAL_SUPPORT to defconfigs.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/uniphier_ld20_defconfig b/configs/uniphier_ld20_defconfig
index b85f528..3fe3758 100644
--- a/configs/uniphier_ld20_defconfig
+++ b/configs/uniphier_ld20_defconfig
@@ -1,6 +1,7 @@
 CONFIG_ARM=y
 CONFIG_ARCH_UNIPHIER=y
 CONFIG_SYS_MALLOC_F_LEN=0x2000
+CONFIG_SPL_SERIAL_SUPPORT=y
 CONFIG_ARCH_UNIPHIER_LD20=y
 CONFIG_MICRO_SUPPORT_CARD=y
 CONFIG_SYS_TEXT_BASE=0x84000000