Fix implicit declaration of function 'eth_[gs]etenv_enetaddr'

...and some other compile warnings.

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/board/sandburst/metrobox/metrobox.c b/board/sandburst/metrobox/metrobox.c
index bd6be3d..fc136c8 100644
--- a/board/sandburst/metrobox/metrobox.c
+++ b/board/sandburst/metrobox/metrobox.c
@@ -32,6 +32,10 @@
 #include <i2c.h>
 #include "../common/ppc440gx_i2c.h"
 #include "../common/sb_common.h"
+#if defined(CONFIG_HAS_ETH0) || defined(CONFIG_HAS_ETH1) || \
+    defined(CONFIG_HAS_ETH2) || defined(CONFIG_HAS_ETH3)
+#include <net.h>
+#endif
 
 void fpga_init (void);