refactor(measured boot): remove unused extern

Change-Id: I4fb7a79c2f31973a3cd181feaface9a42bc3246f
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>

include/drivers/measured_boot/measured_boot.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, Arm Limited. All rights reserved.
+ * Copyright (c) 2020-2021, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -11,9 +11,6 @@
 
 #include <drivers/measured_boot/event_log.h>
 
-/* Platform specific table of image IDs, names and PCRs */
-extern const image_data_t images_data[];
-
 /* Functions' declarations */
 void measured_boot_init(void);
 void measured_boot_finish(void);