UBUNTU: SAUCE: (upstream) netdev/fec: fix phy_speed caculating

BugLink: http://bugs.launchpad.net/bugs/546649
BugLink: http://bugs.launchpad.net/bugs/457878

 - remove duplicated phy_speed caculation
 - fix the phy_speed caculation according to the DataSheet

Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>