libvpx

Fix bug in setting sf->use_square_partition_only.

Fix bug in setting this flag for animated content.
The bug did cause quality to increase because far
more frames are not boosted than boosted.

However, the speed trade off to gain is a lot less
favorable and the behavior was not as intended.

Change-Id: I89fb70419c88b26f40b3534de0481730a1b3fcfa