net: uli526x: Fix unknown storage size error

The variable netdev_ethtool_ops is not referenced, drop it.  However
with gcc-6 or later we fail to even compile as we do not have the
required struct definition in U-Boot.

Cc: Joe Hershberger <joe.hershberger@ni.com>
Signed-off-by: Tom Rini <trini@konsulko.com>

drivers/net/uli526x.c

@@ -166,7 +166,6 @@ static int mode = 8;
 
 /* function declaration -- */
 static int uli526x_start_xmit(struct eth_device *dev, void *packet, int length);
-static const struct ethtool_ops netdev_ethtool_ops;
 static u16 read_srom_word(long, int);
 static void uli526x_descriptor_init(struct uli526x_board_info *, unsigned long);
 static void allocate_rx_buffer(struct uli526x_board_info *);