Fix MISRA rule 8.5 Part 1

Rule 8.5: An external object or function shall be declared
          once in one and only one file.

Fixed for:
	make DEBUG=1 PLAT=fvp LOG_LEVEL=50 all

Change-Id: I2420c58134c280db90706cad2d5e7a190f9f9311
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>

common/desc_image_load.c

 /*
- * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2018, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -10,8 +10,6 @@
 #include <desc_image_load.h>
 
 
-extern bl_mem_params_node_t *bl_mem_params_desc_ptr;
-extern unsigned int bl_mem_params_desc_num;
 
 static bl_load_info_t bl_load_info;
 static bl_params_t next_bl_params;