net/mlx5: Don't rely on interface state bit

The check of MLX5_INTERFACE_STATE_UP is completely useless, because
the FW tracer cleanup is called on every change of the interface
and it ensures that notifier is disabled together with canceling
all the pending works.

Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>