msm: hotplug: Update default fast_lane_load

A value of 99% load catches almost all spikes and keeps spurious
onlinings to an absolute minimum.

Replace all instances of cputime64_t by u64 (see upstream commit
72a4ce340a7ebf39e1c6fdc8f5feb4f974d6c635).
msm: rq_stats: Use u64 for variables, arguments and return vals