libc: Fix all includes in codebase

The codebase was using non-standard headers. It is needed to replace
them by the correct ones so that we can use the new libc headers.

Change-Id: I530f71d9510cb036e69fe79823c8230afe890b9d
Acked-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/include/bl31/ehf.h b/include/bl31/ehf.h
index 1446279..c60b04c 100644
--- a/include/bl31/ehf.h
+++ b/include/bl31/ehf.h
@@ -9,6 +9,7 @@
 
 #ifndef __ASSEMBLY__
 
+#include <cdefs.h>
 #include <stdint.h>
 #include <utils_def.h>