phy: Centralize setting driver module owner

Rather than have each driver set the driver owner field, do it once in
the core code. This will also help with later changes, when the device
structure will move.

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>