net: phy: don't set autoneg if it's not supported

In phy_device_create() we set phydev->autoneg = 1. This isn't changed
even if the PHY doesn't support autoneg. This seems to affect very
few PHY's, and they disable phydev->autoneg in their config_init
callback. So it's more of an improvement, therefore net-next.
The patch also wouldn't apply to older kernel versions because the
link mode bitmaps have been introduced recently.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>