freedreno/a6xx: some register cleanup/updates
Mostly cleanup, except the last patch which documents unknown bits found by the "brute force" method on a650, and for a few of those fields I figured out what they do, like
THREADMODE (use only single wave per SP) ,
SINGLE_SP (use only a single SP),
THREADSIZE_SCALAR (use only a single thread per wave).
Also set the newly documented
SP_PERFCTR_ENABLE register in computerator to fix some perfcntrs.