rockchip: px30: move secure init to separate file

Similar to others like rk3399 and rk3288 move the secure init to a
separate file to unclutter the soc init a bit.

Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Change-Id: Iebb38e24f1c7fe5353f139c896fb8ca769bf9691
diff --git a/plat/rockchip/px30/drivers/pmu/pmu.c b/plat/rockchip/px30/drivers/pmu/pmu.c
index 0a2515d..5f4e64f 100644
--- a/plat/rockchip/px30/drivers/pmu/pmu.c
+++ b/plat/rockchip/px30/drivers/pmu/pmu.c
@@ -22,6 +22,7 @@
 #include <plat_private.h>
 #include <pmu.h>
 #include <px30_def.h>
+#include <secure.h>
 #include <soc.h>
 
 DEFINE_BAKERY_LOCK(rockchip_pd_lock);