fix(platforms): remove platform_core_pos_helper()

Its last user was removed some time ago so it is no longer necessary.

Change-Id: I28264367abd2902ed0d3f207f686538a82a44eba
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
diff --git a/include/plat/common/platform.h b/include/plat/common/platform.h
index faccf31..e10770c 100644
--- a/include/plat/common/platform.h
+++ b/include/plat/common/platform.h
@@ -465,13 +465,6 @@
 void plat_flush_next_bl_params(void);
 
 /*
- * The below function enable Trusted Firmware components like SPDs which
- * haven't migrated to the new platform API to compile on platforms which
- * have the compatibility layer disabled.
- */
-unsigned int platform_core_pos_helper(unsigned long mpidr);
-
-/*
  * Optional function to get SOC version
  */
 int32_t plat_get_soc_version(void);
diff --git a/plat/common/aarch64/plat_common.c b/plat/common/aarch64/plat_common.c
index ba47b30..4423863 100644
--- a/plat/common/aarch64/plat_common.c
+++ b/plat/common/aarch64/plat_common.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014-2024, Arm Limited and Contributors. All rights reserved.
+ * Copyright (c) 2014-2025, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -45,18 +45,6 @@
 {
 }
 
-/*
- * Helper function for platform_get_pos() when platform compatibility is
- * disabled. This is to enable SPDs using the older platform API to continue
- * to work.
- */
-unsigned int platform_core_pos_helper(unsigned long mpidr)
-{
-	int idx = plat_core_pos_by_mpidr(mpidr);
-	assert(idx >= 0);
-	return idx;
-}
-
 #if SDEI_SUPPORT
 /*
  * Function that handles spurious SDEI interrupts while events are masked.