Fix compile warning on lib_ppc/board.c

Signed-off-by: Anatolij Gustschin <agust@denx.de>

include/common.h

@@ -391,7 +391,7 @@ void	icache_disable(void);
 int	dcache_status (void);
 void	dcache_enable (void);
 void	dcache_disable(void);
-void	relocate_code (ulong, gd_t *, ulong);
+void	relocate_code (ulong, gd_t *, ulong) __attribute__ ((noreturn));
 ulong	get_endaddr   (void);
 void	trap_init     (ulong);
 #if defined (CONFIG_4xx)	|| \