ARM: uniphier: move CONFIG_SPL_* to defconfig or select

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>