Replace Rockchip delay timer by generic one

Use the generic delay timer instead of having a specific platform
file for configuring it.

Change-Id: Ifa68b9c97cd96ae1190cee74d22d729af95e4537
diff --git a/plat/rockchip/rk3399/platform.mk b/plat/rockchip/rk3399/platform.mk
index 6d7e134..45064e7f8 100644
--- a/plat/rockchip/rk3399/platform.mk
+++ b/plat/rockchip/rk3399/platform.mk
@@ -57,6 +57,7 @@
                                 drivers/console/console.S                       \
                                 drivers/ti/uart/16550_console.S                 \
                                 drivers/delay_timer/delay_timer.c               \
+                                drivers/delay_timer/generic_delay_timer.c	\
                                 lib/cpus/aarch64/cortex_a53.S                   \
                                 lib/cpus/aarch64/cortex_a72.S                   \
                                 plat/common/aarch64/platform_mp_stack.S         \
@@ -64,7 +65,6 @@
                                 ${RK_PLAT_COMMON}/bl31_plat_setup.c             \
                                 ${RK_PLAT_COMMON}/pmusram/pmu_sram_cpus_on.S	\
 				${RK_PLAT_COMMON}/pmusram/pmu_sram.c		\
-                                ${RK_PLAT_COMMON}/plat_delay_timer.c            \
                                 ${RK_PLAT_COMMON}/plat_pm.c                     \
                                 ${RK_PLAT_COMMON}/plat_topology.c               \
                                 ${RK_PLAT_COMMON}/aarch64/platform_common.c        \