witness: remove ifnet_rw

[kp]

Summary

This lock no longer exists. It was removed in
a60100fdfc106f8966fa572fa72e82b0813c623b

Pointed out by: Dheeraj Kandula <[e-mail]>

[dheerajk_netapp.com]

The ifnet_sxlock lock is still present. Isn't that grabbed during the multicast code path? If so, shouldn't that be added to the lock order?

[kp]

In D31585#712027, @dheerajk_netapp.com wrote:

The ifnet_sxlock lock is still present. Isn't that grabbed during the multicast code path? If so, shouldn't that be added to the lock order?

Possibly, but it's not present right now either.
The entries here are hints of the expected locking order, for witness to check, so if it's not complaining now (and I think it's not) the extra hint isn't needed.