refactor(bl2): make post image handling platform-specific

In certain instances a platform may need to make modifications to an
image after it has been loaded by BL2. The existing common
implementation is a thin wrapper for a more generic arm post image
handler. To enable platforms to make changes to images when
they're loaded, move this into platform code.

Change-Id: I44025391056adb2d8a8eb4ea5984257b02027181
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
diff --git a/plat/arm/css/common/css_bl2_setup.c b/plat/arm/css/common/css_bl2_setup.c
index 002c6eb..1e055c5 100644
--- a/plat/arm/css/common/css_bl2_setup.c
+++ b/plat/arm/css/common/css_bl2_setup.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2023, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -84,3 +84,8 @@
 # endif /* EL3_PAYLOAD_BASE */
 
 #endif /* CSS_USE_SCMI_SDS_DRIVER */
+
+int bl2_plat_handle_post_image_load(unsigned int image_id)
+{
+	return arm_bl2_plat_handle_post_image_load(image_id);
+}