cxgbe(4): Use the correct filter width for T5+.

T5 and above have extra bits for the optional filter fields. This is a
correctness issue and not just a waste because a filter mode valid on a
T4 (36b) may not be valid on a T5+ (40b).

Sponsored by: Chelsio Communications

(cherry picked from commit 0460a45062dfeb98b1f1f7a3a7b9268662b61545)