ARM: UniPhier: make pinmon command optional

Add CONFIG_CMD_PINMON to UniPhier-specific Kconfig and make the
"pinmon" command user-configurable.  This command can be disabled
via the configuration if users do not need it.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/arch/arm/cpu/armv7/uniphier/Makefile b/arch/arm/cpu/armv7/uniphier/Makefile
index 7ceddda..dd57469 100644
--- a/arch/arm/cpu/armv7/uniphier/Makefile
+++ b/arch/arm/cpu/armv7/uniphier/Makefile
@@ -12,7 +12,7 @@
 obj-$(CONFIG_DISPLAY_CPUINFO) += cpu_info.o
 obj-$(CONFIG_BOARD_LATE_INIT) += board_late_init.o
 obj-$(CONFIG_UNIPHIER_SMP) += smp.o
-obj-$(if $(CONFIG_SPL_BUILD),,y) += cmd_pinmon.o
+obj-$(CONFIG_CMD_PINMON) += cmd_pinmon.o
 
 obj-y += board_common.o
 obj-$(CONFIG_PFC_MICRO_SUPPORT_CARD) += support_card.o