ppc: cleanup compiler errors/warnings

Current u-boot top of tree builds with warnings/errors for
the following boards:

ads5121 cpci5200 mecp5200 v38b IAD210 MBX MBX860T NX823
RPXClassic debris PN62

following patch solves this.

Signed-off-by: Heiko Schocher <hs@denx.de>
Acked-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/cpu/mpc512x/cpu.c b/cpu/mpc512x/cpu.c
index be532af..8021bc1 100644
--- a/cpu/mpc512x/cpu.c
+++ b/cpu/mpc512x/cpu.c
@@ -30,6 +30,7 @@
 #include <common.h>
 #include <command.h>
 #include <mpc512x.h>
+#include <net.h>
 #include <netdev.h>
 #include <asm/processor.h>