i40evf: don't delete all the filters

Due to an inverted conditional, the driver was marking all of its MAC
filters for deletion every time set_rx_mode was called. Depending upon
the timing of the calls to set_rx_mode and the processing of the admin
queue, the driver would (accidentally) end up with a varying number of
functional filters.

Correct this logic so that MAC filters are added and removed correctly.
Add a check for the driver's "hardware" MAC address so that this filter
doesn't get removed incorrectly.

Change-ID: Ib3e7c4a5b53df6835f164fe44cb778cb71f8aff8
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Jim Young <james.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>