uniphier: call uniphier_scp_is_running() only when on-chip STM is supported

uniphier_scp_is_running() reads the UNIPHIER_STMBE2COM register,
but it does not exist on all SoCs.

Do not call this function if the on-chip SCP is not supported.

Change-Id: I7c71ca0735e3a8e095c3f22ba6165f82a2986362
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/plat/socionext/uniphier/platform.mk b/plat/socionext/uniphier/platform.mk
index d974584..d31fbe8 100644
--- a/plat/socionext/uniphier/platform.mk
+++ b/plat/socionext/uniphier/platform.mk
@@ -60,6 +60,7 @@
 				plat/common/plat_gicv3.c		\
 				plat/common/plat_psci_common.c		\
 				$(PLAT_PATH)/uniphier_bl31_setup.c	\
+				$(PLAT_PATH)/uniphier_boot_device.c	\
 				$(PLAT_PATH)/uniphier_cci.c		\
 				$(PLAT_PATH)/uniphier_gicv3.c		\
 				$(PLAT_PATH)/uniphier_psci.c		\