DCache timing problem has not been solved yet. DCache structure will be further changed.

* sbuffer: add extra perf counters

* sbuffer: optmize timeout replay check timing

* sbuffer: optmize do_uarch_drain check timing

Now we only compare merge entry's vtag, check will not start until
mergeIdx is generated by PriorityEncoder

* mem, lq: optmize writeback select logic timing

* dcache: replace missqueue reill req arbiter

* dcache: refactor missqueue entry select logic

* mem: add comments for lsq data

* dcache: give amo alu an extra cycle

* sbuffer: optmize sbuffer forward data read timing