plat/arm/sgi: move bl31_platform_setup to board file

For SGI-575 and RD platforms, move bl31_platform_setup handler to
individual board files to allow the platforms to perform board specific
bl31 setup.

Change-Id: Ia44bccc0a7f40a155b33909bcb438a0909b20d42
Signed-off-by: Vijayenthiran Subramaniam <vijayenthiran.subramaniam@arm.com>
diff --git a/plat/arm/board/rde1edge/rde1edge_plat.c b/plat/arm/board/rde1edge/rde1edge_plat.c
index a1b8d62..9eccbc4 100644
--- a/plat/arm/board/rde1edge/rde1edge_plat.c
+++ b/plat/arm/board/rde1edge/rde1edge_plat.c
@@ -1,10 +1,11 @@
 /*
- * Copyright (c) 2018, Arm Limited. All rights reserved.
+ * Copyright (c) 2018-2020, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
 #include <plat/common/platform.h>
+#include <sgi_plat.h>
 
 unsigned int plat_arm_sgi_get_platform_id(void)
 {
@@ -16,3 +17,8 @@
 {
 	return mmio_read_32(SID_REG_BASE + SID_SYSTEM_CFG_OFFSET);
 }
+
+void bl31_platform_setup(void)
+{
+	sgi_bl31_common_platform_setup();
+}