ice: Fix max VLANs available for VF

Legacy VLAN implementation allows for untrusted VF to have 8 VLAN
filters, not counting VLAN 0 filters. Current VLAN_V2 implementation
lowers available filters for VF, by counting in VLAN 0 filter for both
TPIDs.
Fix this by counting only non zero VLAN filters.
Without this patch, untrusted VF would not be able to access 8 VLAN
filters.

Fixes: cc71de8f ("ice: Add support for VIRTCHNL_VF_OFFLOAD_VLAN_V2")
Signed-off-by: Przemyslaw Patynowski <przemyslawx.patynowski@intel.com>
Signed-off-by: Mateusz Palczewski <mateusz.palczewski@intel.com>
Tested-by: Marek Szlosek <marek.szlosek@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>