i40e: fix handling of vf_states variable

Currently we inappropriately clear the vf_states variable with a null
assignment.  This is problematic because we should be using atomic
bitops on this variable and we don't actually want to clear all the
flags.  We should just clear the ones we know we want to clear.
Additionally remove the I40E_VF_STATE_FCOEENA bit because it is no
longer being used.

Signed-off-by: Alan Brady <alan.brady@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>