net: phy: Add more 1000BaseX support detection

Commit "net: phy: Add detection of 1000BaseX link mode support" added
support for not filtering out 1000BaseX mode from the PHY's supported
modes in genphy_config_init, but we have to make a similar change in
genphy_read_abilities in order to actually detect it as a supported mode
in the first place. Add this in.

Signed-off-by: Robert Hancock <hancock@sedsystems.ca>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>