i40evf: properly handle ndo_set_mac_address calls

The driver was not correctly handling calls to its ndo_set_mac_address
method. It did not properly check to see if the override would be
allowed by the PF driver, and never removed the old address from its
filter list.

Add a new flag to the adapter struct which is set if the MAC address is
assigned by the PF. Check this flag and don't allow the MAC address to
be changed if it is set. Search for and properly remove the filter
for the old MAC address when the new one is set.

Change-ID: I817bf620c869c5a80e6a7eab65c9cbad1dc89799
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>