iavf: rename IAVF_VLAN_IS_NEW to IAVF_VLAN_ADDING

iavf: rename IAVF_VLAN_IS_NEW to IAVF_VLAN_ADDING

Rename the IAVF_VLAN_IS_NEW state to IAVF_VLAN_ADDING to better
describe what the state represents: an ADD request has been sent to
the PF and is waiting for a response.

This is a pure rename with no behavioral change, preparing for a
cleanup of the VLAN filter state machine.

Signed-off-by: Petr Oros <poros@redhat.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20260427-jk-iwl-net-petr-oros-fixes-v1-1-cdcb48303fd8@intel.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>