net/mlx5: E-switch, Introduce and use vlan rule config helper

Between legacy mode and switchdev mode, only two fields are changed,
vlan_tag and flow action.
Hence to avoid duplicte code between two modes, introduce and and use
helper function to configure allowed VLAN rule.

While at it, get rid of duplicate debug message.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Vu Pham <vuhuong@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>