Replace some memset call by zeromem

Replace all use of memset by zeromem when zeroing moderately-sized
structure by applying the following transformation:
memset(x, 0, sizeof(x)) => zeromem(x, sizeof(x))

As the Trusted Firmware is compiled with -ffreestanding, it forbids the
compiler from using __builtin_memset and forces it to generate calls to
the slow memset implementation. Zeromem is a near drop in replacement
for this use case, with a more efficient implementation on both AArch32
and AArch64.

Change-Id: Ia7f3a90e888b96d056881be09f0b4d65b41aa79e
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>
diff --git a/drivers/io/io_memmap.c b/drivers/io/io_memmap.c
index fe39652..53af4f6 100644
--- a/drivers/io/io_memmap.c
+++ b/drivers/io/io_memmap.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2014-2017, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -33,6 +33,7 @@
 #include <io_driver.h>
 #include <io_storage.h>
 #include <string.h>
+#include <utils.h>
 
 /* As we need to be able to keep state for seek, only one file can be open
  * at a time. Make this a structure and point to the entity->info. When we
@@ -231,7 +232,7 @@
 	entity->info = 0;
 
 	/* This would be a mem free() if we had malloc.*/
-	memset((void *)&current_file, 0, sizeof(current_file));
+	zeromem((void *)&current_file, sizeof(current_file));
 
 	return 0;
 }