cxgbe: convert to timer_setup() LinuxKPI

[bz]

Summary

Switch from init_timer() and manual setup of structure fields, right
past setup_timer and timer_from directly to timer_setup and
timer_container_of as part of trying to clear up the Linux pre-4.15
timer KPI from LinuxKPI.

The 2nd timer I am not sure about but it seems unused?

MFC after: 3 days

Test Plan

I HAVE NOT TESTED

[emaste]

sys/dev/cxgbe/iw_cxgbe/qp.c

1888–1890

why this rather than just removing init_timer?

[emaste]

superseded by 05057380ca392b29d33a4d362936e8af81101685 I believe

[bz]

sys/dev/cxgbe/iw_cxgbe/qp.c

1888–1890

For @np and @jhb to check that it is so, as they understand the underlying data structures and events hopefully better than me. I was just wondering why it was there in first place.

[bz]

Superseeded by @jhb's work. Thanks a lot!