Arnd Bergmann asked that get_phy_device() returns either NULL or the error
value,  not both on error.  Do as he said, return ERR_PTR(-ENODEV) instead
of NULL when the PHY ID registers read as  all ones.
Suggested-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NSergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>