Protect the "ratectl_ch" callout in the "run" driver by the "run"
softc's "sc->sc_mtx" mutex. Currently the callout was marked
multi-processor safe, which is fine, but it is better to
start/stop/reset callouts while holding the "run" drivers own
mutex. While at it add a missing "ULL" at end of the 64-bit unsigned
integer constant.

MFC after:	1 week