phylib: SIOCGMIIREG/SIOCSMIIREG: allow access to all mdio addresses

phylib would silently ignore the phy_id argument to these ioctls and
perform the read/write with the active phydev address, whereas most
non-phylib drivers seem to allow access to all mdio addresses
(E.G. pcnet_cs).

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>