ixgbe: Update the usage of orig_autoc to be more consistent

The orig_autoc variable tracks the original setting of the autonegotiate
state prior to trying a new speed.  The usage is inconsistent and not very
maintainable.  This patch updates the usage to make it more consistent.

Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>