iavf: do not track VLAN 0 filters

When an interface with the maximum number of VLAN filters is brought up,
a spurious error is logged:

    [257.483082] 8021q: adding VLAN 0 to HW filter on device enp0s3
    [257.483094] iavf 0000:00:03.0 enp0s3: Max allowed VLAN filters 8. Remove existing VLANs or disable filtering via Ethtool if supported.

The VF driver complains that it cannot add the VLAN 0 filter.

On the other hand, the PF driver always adds VLAN 0 filter on VF
initialization. The VF does not need to ask the PF for that filter at
all.

Fix the error by not tracking VLAN 0 filters altogether. With that, the
check added by commit 0e710a3f ("iavf: Fix VF driver counting VLAN 0
filters") in iavf_virtchnl.c is useless and might be confusing if left as
it suggests that we track VLAN 0.

Fixes: 0e710a3f ("iavf: Fix VF driver counting VLAN 0 filters")
Signed-off-by: Ahmed Zaki <ahmed.zaki@intel.com>
Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>