Clean usage of void pointers to access symbols

Void pointers have been used to access linker symbols, by declaring an
extern pointer, then taking the address of it. This limits symbols
values to aligned pointer values. To remove this restriction an
IMPORT_SYM macro has been introduced, which declares it as a char
pointer and casts it to the required type.

Change-Id: I89877fc3b13ed311817bb8ba79d4872b89bfd3b0
Signed-off-by: Joel Hutton <Joel.Hutton@Arm.com>
diff --git a/bl1/bl1_private.h b/bl1/bl1_private.h
index 6ac3b8c..42a74d2 100644
--- a/bl1/bl1_private.h
+++ b/bl1/bl1_private.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2018, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -8,18 +8,16 @@
 #define __BL1_PRIVATE_H__
 
 #include <types.h>
+#include <utils_def.h>
 
 /*******************************************************************************
  * Declarations of linker defined symbols which will tell us where BL1 lives
  * in Trusted ROM and RAM
  ******************************************************************************/
-extern uintptr_t __BL1_ROM_END__;
-#define BL1_ROM_END (uintptr_t)(&__BL1_ROM_END__)
+IMPORT_SYM(uintptr_t, __BL1_ROM_END__,   BL1_ROM_END);
 
-extern uintptr_t __BL1_RAM_START__;
-extern uintptr_t __BL1_RAM_END__;
-#define BL1_RAM_BASE (uintptr_t)(&__BL1_RAM_START__)
-#define BL1_RAM_LIMIT (uintptr_t)(&__BL1_RAM_END__)
+IMPORT_SYM(uintptr_t, __BL1_RAM_START__, BL1_RAM_BASE);
+IMPORT_SYM(uintptr_t, __BL1_RAM_END__,   BL1_RAM_LIMIT);
 
 /******************************************
  * Function prototypes