Test: Remove unused code from helpers file

Change-Id: I86dd5a803a0d4aa93416864a73bfef05a5c6ffdb
Signed-off-by: Raef Coles <raef.coles@arm.com>
diff --git a/test/framework/test_framework_helpers.h b/test/framework/test_framework_helpers.h
index a4f7a3b..1cec7e0 100644
--- a/test/framework/test_framework_helpers.h
+++ b/test/framework/test_framework_helpers.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2021, Arm Limited. All rights reserved.
+ * Copyright (c) 2017-2022, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  *
@@ -28,15 +28,6 @@
 };
 
 /**
- * \brief Translates asset permissions into a string.
- *
- * \param[in] permissions  Asset permissions value.
- *
- * \return asset permissions as string.
- */
-const char *asset_perms_to_str(uint8_t permissions);
-
-/**
  * \brief Sets the the text color in the serial port.
  *
  * \param[in] color_id  Serial foreground color.