Fix fallout from the e500 math integration.

from Steve Papacharalambous.

libm/powerpc/classic/s_copysign.c

@@ -23,7 +23,7 @@
 *******************************************************************************/
 
 #include <math.h>
-#include "../fp_private.h"
+#include "../../fp_private.h"
 
 /*******************************************************************************
 *                                                                              *