amcvideodec: Expose non-GL formats on Lollipop+

Submitted by Olivier Crête @ocrete

Link to original bug (#768264)

Description

Before Lollipop, the only way to know which format a decoder would decode into was to start decoding, and then just before getting the first frame, we could get the format. Since Lollipop, you can get the output format by just doing a configure(), this only requires the mime type of the codec and the resolution. I've tried just using 640x480 as I assume all machines should do that. The second assumption is that the output format is the same irrelevant of the resolution. This also means that although a decoder can in theory output many formats, we can know exactly which one it will output for each input format.

Just as I'm attaching the patches, I'm thinking that maybe we should also move the gl_output_only flag to be per input format.