phy_device: Move phy attributes into phy_device

The mdio_bus exports three attributes:

- PHY ID is the unique 32-bits identifier for a MDIO device implementing
  standard MII registers MII_PHYSID1/2, which is not guaranteed to be the
  case for non-standard compliant devices (e.g: Ethernet switches)

- PHY interface describes the data-path of the PHY/MDIO device, which is
  not strictly a PHY thing, but is required and needed for PHY devices to
  function, a MDIO device could be a control device exclusively

- PHY has fixups describes what the PHY driver may have done, so
  completely PHY specific

These are all phy attributes, not generic mdio attributes. So move the
attributes into the phy device code.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>