msm_mpdecision:  access rq_stats directly and eliminate msm_rq_stats
msm_rq_stats is for enabling access to rq_stats from user space and
comes with many spinlocks and mutexes as an overhead. Since we can
more efficiently access rq_stats directly from kernel-based mpdecision,
we can eliminate msm_rq_stats and the its overhead. Yay!