net/mlx5: Bridge, rename filter fg to vlan_filter

Following patches in series introduce new qinq filtering group. To improve
readability rename the existing group in function, variable and definition
names to include "vlan" in order to make it easy to distinguish from
upcoming qinq group.

Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>