i40e: Prevent falling to promiscuous if the VF is not trusted

With this change a non trusted VF can never fall to promiscuous
mode when there is no room for a MAC/VLAN filter.

Change-Id: I8a155aa25c0bcdc6093414920c9ade4ee0bd20e8
Signed-off-by: Anjali Singhai Jain <anjali.singhai@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>