Replace shift with multiply
Replace shift with multiply

To avoid left shift of negative values.

BUG=aomedia:678

Change-Id: I8dacf99f162771a58bef1f839cafd0be9a8f5e86

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