igb: remove disable_av variable from mac_info struct
The disable_av variable is never used by the driver and provides no value as
it is likely a leftover debugging variable. I have removed it and replaced
the one spot that checked for it with a check for a valid address.
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>