net/mlx5e: Support accept action

Support TC generic 'accept' action in mlx5 by introducing
MLX5_ESW_ATTR_FLAG_ACCEPT attribute flag. Flag has similar semantics to
existing MLX5_ESW_ATTR_FLAG_SLOW_PATH flag, however, dedicated flag is
required because existing 'slow path' flag can be flipped by tunneling
subsystem when neighbor changes state.

Introduce new helper function mlx5_esw_attr_flags_skip() to check whether
attribute flags for 'slow path' or 'accept' action are set and use it in
eswitch code instead of direct bit manipulation.

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