ARM: UniPhier: set MACH_PH1_PRO4 as default SoC

One disadvantage of commit a26cd049 (arch: Make board selection
choices optional) is that Kconfig could create such an insane
.config file that no board is selected.

As PH1-Pro4 is the main stream of UniPhier SoC family, rip off the
"optional" again in favor of PH1-Pro4 as the default SoC.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/arm/mach-uniphier/Kconfig

@@ -8,7 +8,7 @@ config UNIPHIER_SMP
 
 choice
 	prompt "UniPhier SoC select"
-	optional
+	default MACH_PH1_PRO4
 
 config MACH_PH1_PRO4
 	bool "PH1-Pro4"

configs/ph1_pro4_defconfig

 CONFIG_ARM=y
 CONFIG_ARCH_UNIPHIER=y
 CONFIG_SPL_DM=y
-CONFIG_MACH_PH1_PRO4=y
 CONFIG_PFC_MICRO_SUPPORT_CARD=y
 CONFIG_SYS_TEXT_BASE=0x84000000
 CONFIG_DEFAULT_DEVICE_TREE="uniphier-ph1-pro4-ref"