wandboard: Fix sparse warning

Add a prototype for board_phy_config() to fix the following sparse warning:

wandboard.c:200:5: warning: symbol 'board_phy_config' was not declared. Should it be static?

Cc: Joe Hershberger <joe.hershberger@ni.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
diff --git a/board/wandboard/wandboard.c b/board/wandboard/wandboard.c
index dbced1c..6918614 100644
--- a/board/wandboard/wandboard.c
+++ b/board/wandboard/wandboard.c
@@ -25,6 +25,7 @@
 #include <miiphy.h>
 #include <netdev.h>
 #include <linux/fb.h>
+#include <phy.h>
 
 DECLARE_GLOBAL_DATA_PTR;