Change left shift to multiply
Change left shift to multiply

Negative distortion is used in trellis quant process for RDcost
computation, this change avoids compiler warning on "left shift
of negative values".

Change-Id: Iaea0ffebb6c9236e779e36301fbc69b180be1f3d

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom