e100: fix typo in MDI/MDI-X eeprom check in e100_phy_init

Although it doesn't explicitly say so, commit 60ffa478 ("e100:
Fix MDIO/MDIO-X") appears to be intended to revert the earlier commit
64895145

 ("e100: fixed e100 MDI/MDI-X issues").  However,
careful examination reveals that the attempted revert actually
_inverted_ the test for eeprom_mdix_enabled.  That is bound to program
a few PHYs incorrectly...

https://bugzilla.redhat.com/show_bug.cgi?id=1156417

Signed-off-by: "John W. Linville" <linville@tuxdriver.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>