cxgbe(4): Use correct argument in call to hashdestroy.

This fixes a panic on driver module unload.

Fixes: 24b98f288d11 cxgbe(4): Overhaul CLIP (Compressed Local IPv6) table management.
Sponsored by: Chelsio Communications

(cherry picked from commit 740d722def71905dd74a622acce1561701ccbec6)