cam iosched: Limit the quanta default to hz if it's below 200

The cam_iosched_ticker() can't be scheduled more than once per tick.
Some limiters depend on quanta matching the number of calls per second
to enforce the proper limits. Limit the quanta to no faster than 1 per
clock tick. This fixes some features when running in VMs where the
default HZ is 100.

PR: 221953
Obtained from: ElectroBSD
Differential Revision: https://reviews.freebsd.org/D12337
Submitted by: Fabian Keil