Fix compile error caused by incorrect function return type

Rename int mii_init(void) to void mii_init(void) for idmr
ColdFire platform

Signed-off-by: TsiChung Liew <Tsi-Chung.Liew@freescale.com>

board/idmr/mii.c

@@ -200,7 +200,7 @@ int mii_discover_phy(struct eth_device *dev)
 }
 #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)
 {