libc: Adapt to TFTF

Add support for functions used in TFTF but not in TF-A.

Replaced calls to plat_panic_handler with calls to panic, since there is no
implementation of the former in TFTF.

Change-Id: Ic10de2c6e749db97b932cd7ffbb6067b5befe914
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
diff --git a/include/lib/libc/uuid.h b/include/lib/libc/uuid.h
index 934fb4f..bdefb91 100644
--- a/include/lib/libc/uuid.h
+++ b/include/lib/libc/uuid.h
@@ -34,8 +34,8 @@
 #ifndef _SYS_UUID_H_
 #define _SYS_UUID_H_
 
-#include <sys/cdefs.h>
-#include <sys/_stdint.h>
+#include <cdefs.h>
+#include <stdint.h>
 
 /* Length of a node address (an IEEE 802 address). */
 #define	_UUID_NODE_LEN		6