PPC32: Fix compile warnings in some programs used in the build process

arch/ppc/boot/utils/addnote.c

@@ -14,6 +14,7 @@
  * Usage: addnote zImage
  */
 #include <stdio.h>
+#include <stdlib.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <string.h>

arch/ppc/boot/utils/hack-coff.c

@@ -11,8 +11,10 @@
  * 2 of the License, or (at your option) any later version.
  */
 #include <stdio.h>
+#include <stdlib.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <string.h>
 #include "rs6000.h"
 
 #define AOUT_MAGIC	0x010b

arch/ppc/boot/utils/mknote.c

@@ -11,6 +11,7 @@
  */
 
 #include <stdio.h>
+#include <string.h>
 
 #define PL(x) printf("%c%c%c%c", ((x)>>24)&0xff, ((x)>>16)&0xff, ((x)>>8)&0xff, (x)&0xff );