net/mlx5e: Deny VLAN rewrite if there is no VLAN header match

Rewrite of the packet in the VLAN offset may corrupt the packet if it's
not VLAN tagged. Deny the rewrite in this case.

Fixes: 37410902874c ("net/mlx5e: Support VLAN modify action")
Signed-off-by: Eli Britstein <elibr@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>