smsc95xx: remove redundant function arguments

This patch removes arguments netdev and phy_id from the functions
smsc95xx_mdio_read_nopm and smsc95xx_mdio_write_nopm.  Both removed
arguments are recovered from a new argument `struct usbnet *dev`.

Signed-off-by: Andre Edich <andre.edich@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>