plat/rockchip: Use common gicv2.mk

Compiling BL31 for the Rockchip platform now produces a message about
the deprecation of gic_common.c.
Follow the advice and use include gicv2.mk instead.

Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Change-Id: I396b977d57975dba27cfed801ad5264bbbde2b5e
diff --git a/plat/rockchip/rk3368/platform.mk b/plat/rockchip/rk3368/platform.mk
index e787293..e6c62de 100644
--- a/plat/rockchip/rk3368/platform.mk
+++ b/plat/rockchip/rk3368/platform.mk
@@ -4,6 +4,8 @@
 # SPDX-License-Identifier: BSD-3-Clause
 #
 
+include drivers/arm/gic/v2/gicv2.mk
+
 RK_PLAT			:=	plat/rockchip
 RK_PLAT_SOC		:=	${RK_PLAT}/${PLAT}
 RK_PLAT_COMMON		:=	${RK_PLAT}/common
@@ -20,9 +22,7 @@
 				-I${RK_PLAT_SOC}/drivers/ddr/			\
 				-I${RK_PLAT_SOC}/include/
 
-RK_GIC_SOURCES         :=	drivers/arm/gic/common/gic_common.c		\
-				drivers/arm/gic/v2/gicv2_main.c			\
-				drivers/arm/gic/v2/gicv2_helpers.c		\
+RK_GIC_SOURCES         :=	${GICV2_SOURCES}				\
 				plat/common/plat_gicv2.c			\
 				${RK_PLAT}/common/rockchip_gicv2.c