ARM: uniphier: make SPL optional for ARVv8 SoCs

We may want to run different firmware before running U-Boot.  For
example, ARM Trusted Firmware runs before U-Boot, making U-Boot
a non-secure world boot loader.  In this case, the SoC might be
initialized there, which enables us to skip SPL entirely.

This commit removes "select SPL" to make it configurable.  This
also enables the Multi SoC support for the UniPhier ARMv8 SoCs.
(CONFIG_ARCH_UNIPHIER_V8_MULTI)  Thanks to the driver model and
Device Tree, the U-Boot proper part is now written in a generic way.
The board/SoC parameters reside in DT.  The Multi SoC support
increases the memory footprint a bit, but the U-Boot proper does
not have strict memory constraint.  This will mitigate the per-SoC
(sometimes per-board) defconfig burden.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/configs/uniphier_ld20_defconfig b/configs/uniphier_ld20_defconfig
index 302b68a..d352f2e 100644
--- a/configs/uniphier_ld20_defconfig
+++ b/configs/uniphier_ld20_defconfig
@@ -2,12 +2,13 @@
 CONFIG_ARCH_UNIPHIER=y
 CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_SPL_SERIAL_SUPPORT=y
-CONFIG_ARCH_UNIPHIER_LD20=y
+CONFIG_ARCH_UNIPHIER_LD20_SINGLE=y
 CONFIG_MICRO_SUPPORT_CARD=y
 CONFIG_SYS_TEXT_BASE=0x84000000
 CONFIG_DEFAULT_DEVICE_TREE="uniphier-ld20-ref"
 # CONFIG_ARCH_FIXUP_FDT_MEMORY is not set
 CONFIG_BOARD_LATE_INIT=y
+CONFIG_SPL=y
 CONFIG_SPL_NOR_SUPPORT=y
 CONFIG_HUSH_PARSER=y
 # CONFIG_CMD_XIMG is not set