[CfL] Fix subsampling overflow in HBD 4:4:0
[CfL] Fix subsampling overflow in HBD 4:4:0

BUG=aomedia:994

Change-Id: I0fa9d48487256655798dbdd64acad523e84557c6

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