phy: keep pause flags in phy driver features

genphy_config_init() masked out pause flags set in phy driver structure.
Pause flags needs to be preserved in phydev->supported &
phydev->advertising.

Signed-off-by: Woojung Huh <woojung.huh@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>