net: w5100: remove unused is_w5200()

The is_w5200() function is not used anymore by the commit which adds
the W5500 support.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Mike Sinkovsky <msink@permonline.ru>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/wiznet/w5100.c

@@ -173,11 +173,6 @@ struct w5100_priv {
 	struct work_struct restart_work;
 };
 
-static inline bool is_w5200(struct w5100_priv *priv)
-{
-	return priv->ops->chip_id == W5200;
-}
-
 /************************************************************************
  *
  *  Lowlevel I/O functions