e1000e: don't poke PHY registers to retreive link status

Apparently poking the link status registers when autonegotiation
is running on the PHY might botch the PHY link on 80003es2lan
devices. While this is a very rare condition we can completely
avoid it alltogether by just using the MAC link bits to provide
the proper information to ethtool.

Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>