Fix compile error caused by incorrect function return type

Rename int mii_init(void) to void mii_init(void)

Signed-off-by: TsiChung Liew <Tsi-Chung.Liew@freescale.com>
diff --git a/board/cobra5272/mii.c b/board/cobra5272/mii.c
index d0a4a39..b30ba80 100644
--- a/board/cobra5272/mii.c
+++ b/board/cobra5272/mii.c
@@ -200,7 +200,7 @@
 }
 #endif				/* CFG_DISCOVER_PHY */
 
-int mii_init(void) __attribute__((weak,alias("__mii_init")));
+void mii_init(void) __attribute__((weak,alias("__mii_init")));
 
 void __mii_init(void)
 {