iavf: refactor VLAN filter states

The VLAN filter states are currently being saved as individual bits.
This is error prone as multiple bits might be mistakenly set.

Fix by replacing the bits with a single state enum. Also, add an
"ACTIVE" state for filters that are accepted by the PF.

Signed-off-by: Ahmed Zaki <ahmed.zaki@intel.com>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>