fix199: issue caused by using g_aucLog2 in 12b reshaping
- g_aucLog2 can only take values <128. use function floorLog2() instead.
- disable HDR reshaping for bitdepth !=10 for now to prevent unexpected results since current HDR reshaping is designed from LumaLevelToDeltaQP mapping that is only defined at 10bit as well. Further study for 12bit support is on going.