bl1: add bl1_plat_handle_{pre,post}_image_load()

Just like bl2_, add pre/post image load handlers for BL1.  No argument
is needed since BL2 is the only image loaded by BL1.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/plat/common/platform_helpers_default.c b/plat/common/platform_helpers_default.c
index 597a585..ce1a731 100644
--- a/plat/common/platform_helpers_default.c
+++ b/plat/common/platform_helpers_default.c
@@ -12,6 +12,8 @@
  */
 
 #pragma weak plat_error_handler
+#pragma weak bl1_plat_handle_pre_image_load
+#pragma weak bl1_plat_handle_post_image_load
 #pragma weak bl2_plat_preload_setup
 #pragma weak bl2_plat_handle_pre_image_load
 #pragma weak bl2_plat_handle_post_image_load
@@ -23,6 +25,16 @@
 		wfi();
 }
 
+int bl1_plat_handle_pre_image_load(void)
+{
+	return 0;
+}
+
+int bl1_plat_handle_post_image_load(void)
+{
+	return 0;
+}
+
 void bl2_plat_preload_setup(void)
 {
 }