net/mlx5: E-switch, Annotate termtbl_mutex mutex destroy

Annotate mutex destroy to keep it symmetric to init sequence.
It should be destroyed after its users (representor netdevices) are
destroyed in below flow.

esw_offloads_disable()
  esw_offloads_unload_rep()

Hence, initialize the mutex before creating the representors which uses
it.

Reviewed-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Bodong Wang <bodong@mellanox.com>
Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>