igbvf: be sane about random MAC addresses

Tighten up some of the code surrounding MAC addresses. Since the PF is
now giving all zeros instead of a random address, check for this case
and generate a random address. This ensures that we always know when we
have a random address and udev won't get upset about it.

Additionally, tighten up some of the log messages and clean up the
formatting.

Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
CC: Andy Gospodarek <andy@greyhouse.net>
CC: Stefan Assmann <sassmann@kpanic.de>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Tested-by: Stefan Assmann <sassmann@redhat.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>