cam iosched: Limit the quanta default to hz if it's below 200
Previously the quanta default was always 200 while hz defaults
to 100 when running in a vm.
The cam_iosched_ticker() can't be scheduled more than once per tick
and some of the limiters depend on quanta matching the number of calls
per second to enforce the proper limits.
PR: 221953
Obtained from: ElectroBSD