Skip unnecessary search of identical frames

vp8_get_compressed_data() was defeating logic in
encode_frame_to_datarate() that determined the reference buffers to
search and forcing all frames to be eligible to search. In cases
where buffers have identical contents, this is unnecessary extra
work.

Change-Id: I9e667ac39128ae32dc455a3db4c62e3efce6f114
1 file changed