net/mlx5e: Avoid unbounded peer devices when unpairing TC hairpin rules

If the peer device was already unbound, then do not attempt to modify
it's resources, otherwise we will crash on dereferencing non-existing
device.

Fixes: 5c65c564

 ("net/mlx5e: Support offloading TC NIC hairpin flows")
Signed-off-by: Alaa Hleihel <alaa@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>