Prevent overflow in model_rd_from_sse
Prevent overflow in model_rd_from_sse

BUG=aomedia:2067

Change-Id: I50637991df75ea0d67f028ec0f5ed45477f677c0

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