Implement a leaner printf for Trusted Firmware

This patch implements a "tf_printf" which supports only the commonly
used format specifiers in Trusted Firmware, which uses a lot less
stack space than the stdlib printf function.

Fixes ARM-software/tf-issues#116

Change-Id: I7dfa1944f4c1e634b3e2d571f49afe02d109a351
diff --git a/bl2/bl2_main.c b/bl2/bl2_main.c
index d96e199..70b688a 100644
--- a/bl2/bl2_main.c
+++ b/bl2/bl2_main.c
@@ -35,7 +35,6 @@
 #include <debug.h>
 #include <platform.h>
 #include <platform_def.h>
-#include <stdio.h>
 #include "bl2_private.h"
 
 /*******************************************************************************
@@ -196,7 +195,7 @@
 	/* Perform platform setup in BL2 */
 	bl2_platform_setup();
 
-	printf("BL2 %s\n\r", build_message);
+	tf_printf("BL2 %s\n\r", build_message);
 
 	/*
 	 * Load the subsequent bootloader images