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/bl1/bl1_main.c b/bl1/bl1_main.c
index 91b5f0b..fe09070 100644
--- a/bl1/bl1_main.c
+++ b/bl1/bl1_main.c
@@ -177,13 +177,13 @@
 
 	INFO("BL1: Loading BL2\n");
 
-#if LOAD_IMAGE_V2
-	err = bl1_plat_handle_pre_image_load();
+	err = bl1_plat_handle_pre_image_load(BL2_IMAGE_ID);
 	if (err) {
 		ERROR("Failure in pre image load handling of BL2 (%d)\n", err);
 		plat_error_handler(err);
 	}
 
+#if LOAD_IMAGE_V2
 	err = load_auth_image(BL2_IMAGE_ID, image_info);
 #else
 	/* Load the BL2 image */
@@ -200,14 +200,14 @@
 		plat_error_handler(err);
 	}
 
-#if LOAD_IMAGE_V2
 	/* Allow platform to handle image information. */
-	err = bl1_plat_handle_post_image_load();
+	err = bl1_plat_handle_post_image_load(BL2_IMAGE_ID);
 	if (err) {
 		ERROR("Failure in post image load handling of BL2 (%d)\n", err);
 		plat_error_handler(err);
 	}
 
+#if LOAD_IMAGE_V2
 	/*
 	 * Create a new layout of memory for BL2 as seen by BL1 i.e.
 	 * tell it the amount of total and free memory available.