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/bl31_zynqmp_setup.c b/plat/xilinx/zynqmp/bl31_zynqmp_setup.c
index 50fd67b..c99d1b1 100644
--- a/plat/xilinx/zynqmp/bl31_zynqmp_setup.c
+++ b/plat/xilinx/zynqmp/bl31_zynqmp_setup.c
@@ -239,6 +239,8 @@
 		panic();
 	}
 #endif
+
+	custom_runtime_setup();
 }
 
 /*