sky2: flow control negotiation for Yukon-FE

The Yukon-FE chip doesn't do gigabit and has a differen PHY internally.
On this chip, phy status register doesn't properly reflect the result
of flow control negotiation. To workaround the problem and avoid having
to have so much chip dependent code; compute the result of flow control
by looking at the local and remote advertised bits.

Signed-off-by: Stephen Hemmminger <shemminger@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>