net: ethernet: ti: cpsw_ale: add cpsw_ale_vlan_del_modify()

Add/export cpsw_ale_vlan_del_modify() and use it in cpsw_switchdev instead
of generic cpsw_ale_del_vlan() to avoid mixing 8021Q and switchdev VLAN
offload. This is preparation patch equired by follow up changes.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>