refactor(bl)!: remove unused plat_try_next_boot_source

The plat_try_next_boot_source() API is not used by any upstream platform
and not used by platforms that asked for this API. It is then removed.
It will be replaced with a more generic interface in next patch.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I298c7acace8c5efb3c66422d8d9280ecd08e5ade
diff --git a/plat/common/plat_bl_common.c b/plat/common/plat_bl_common.c
index 89b77ba..a603f2b 100644
--- a/plat/common/plat_bl_common.c
+++ b/plat/common/plat_bl_common.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2020, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2018-2024, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -24,7 +24,6 @@
 #pragma weak bl2_plat_preload_setup
 #pragma weak bl2_plat_handle_pre_image_load
 #pragma weak bl2_plat_handle_post_image_load
-#pragma weak plat_try_next_boot_source
 #pragma weak plat_get_enc_key_info
 #pragma weak plat_is_smccc_feature_available
 #pragma weak plat_get_soc_version
@@ -69,11 +68,6 @@
 	return 0;
 }
 
-int plat_try_next_boot_source(void)
-{
-	return 0;
-}
-
 /*
  * Weak implementation to provide dummy decryption key only for test purposes,
  * platforms must override this API for any real world firmware encryption