rockchip: Use common crash console functions

This platform depends on weak functions defined in
``plat/common/aarch64/platform_helpers.S`` that are going to be removed.

Change-Id: I5104d091c32271d77ed9690e9dc257c061289def
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/plat/rockchip/rk3399/platform.mk b/plat/rockchip/rk3399/platform.mk
index 9120419..eccf1cc 100644
--- a/plat/rockchip/rk3399/platform.mk
+++ b/plat/rockchip/rk3399/platform.mk
@@ -32,6 +32,7 @@
 
 PLAT_BL_COMMON_SOURCES	:=	lib/xlat_tables/xlat_tables_common.c	\
 				lib/xlat_tables/aarch64/xlat_tables.c	\
+				plat/common/aarch64/crash_console_helpers.S \
 				plat/common/plat_psci_common.c
 
 BL31_SOURCES	+=	${RK_GIC_SOURCES}				\