feat(zynqmp): add hooks for custom runtime setup

Add runtime setup hooks (via custom_runtime_setup()) for low level
operations related to setting up the system to correct state.

Change-Id: I4af7050dba2ee2446366d482bef5f5c5dde4bddf
Signed-off-by: Amit Nagal <amit.nagal@amd.com>
Signed-off-by: Akshay Belsare <akshay.belsare@amd.com>
diff --git a/plat/xilinx/zynqmp/include/custom_svc.h b/plat/xilinx/zynqmp/include/custom_svc.h
index ef0eb67..7ccde24 100644
--- a/plat/xilinx/zynqmp/include/custom_svc.h
+++ b/plat/xilinx/zynqmp/include/custom_svc.h
@@ -15,5 +15,6 @@
 
 void custom_early_setup(void);
 void custom_mmap_add(void);
+void custom_runtime_setup(void);
 
 #endif /* CUSTOM_SVC_H */