igbvf: Allow VF driver to correctly recognize failure to set mac

The VF driver was not correctly recognizing that it did not correctly set
it's mac address.  As a result the VF driver was unable to receive network
traffic until being unloaded and reloaded.  The issue was root caused to
the fact that the CTS bit was not taken into account when checking for the
request being NAKed.

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>