Add image_id to bl1_plat_handle_post/pre_image_load()

This patch adds an argument to bl1_plat_post/pre_image_load() APIs
to make it more future proof. The default implementation of
these are moved to `plat_bl1_common.c` file.

These APIs are now invoked appropriately in the FWU code path prior
to or post image loading by BL1 and are not restricted
to LOAD_IMAGE_V2.

The patch also reorganizes some common platform files. The previous
`plat_bl2_el3_common.c` and `platform_helpers_default.c` files are
merged into a new `plat_bl_common.c` file.

NOTE: The addition of an argument to the above mentioned platform APIs
is not expected to have a great impact because these APIs were only
recently added and are unlikely to be used.

Change-Id: I0519caaee0f774dd33638ff63a2e597ea178c453
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
diff --git a/plat/common/plat_bl1_common.c b/plat/common/plat_bl1_common.c
index b92cf54..cee34ae 100644
--- a/plat/common/plat_bl1_common.c
+++ b/plat/common/plat_bl1_common.c
@@ -9,6 +9,7 @@
 #include <bl_common.h>
 #include <debug.h>
 #include <errno.h>
+#include <platform.h>
 #include <platform_def.h>
 
 /*
@@ -21,6 +22,8 @@
 #pragma weak bl1_plat_set_ep_info
 #pragma weak bl1_plat_get_image_desc
 #pragma weak bl1_plat_fwu_done
+#pragma weak bl1_plat_handle_pre_image_load
+#pragma weak bl1_plat_handle_post_image_load
 
 
 unsigned int bl1_plat_get_next_image_id(void)
@@ -35,6 +38,16 @@
 
 }
 
+int bl1_plat_handle_pre_image_load(unsigned int image_id)
+{
+	return 0;
+}
+
+int bl1_plat_handle_post_image_load(unsigned int image_id)
+{
+	return 0;
+}
+
 /*
  * Following is the default definition that always
  * returns BL2 image details.