cxgbe: Only run ktls_tick when NIC TLS is enabled.

cxgbe: Only run ktls_tick when NIC TLS is enabled.

Previously the body of ktls_tick was a nop when NIC TLS was disabled,
but the callout was still scheduled consuming power on otherwise-idle
systems with Chelsio T6 adapters.  Now the callout only runs while NIC
TLS is enabled on at least one interface of an adapter.

Reported by:	mav
Reviewed by:	np, mav
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D32491

(cherry picked from commit ef3f98ae4778a8d4463166c5ff3c7831099c6048)