Simplify nested ifs in encode_rd_sb_row.
Simplify nested ifs in encode_rd_sb_row.

The logic is equivalent.

Change-Id: I8d32140b2b625cd161717d0b5729024a334a89de

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