VP9: move loopfilter build masks to decode loop

The loopfilter masks are now built in the decode loop.
This is done so we can eventually reduce the number of
MODE_INFO structs required by the decoder.

The encoder builds the masks for the entire frame prior
to calling the loopfilter.

Change-Id: Ia2146b07e0acb8c50203e586dfae0c4c5b316f11
7 files changed