[rbp] Fix bug with CPicture::CreateTiledThumb and texture pipeline

The decode to texture pipeline results in the decoded pixels not being available to xbmc.
The pixels are required for CPicture::CreateTiledThumb, so provide an extra parameter to request that
Merge pull request #3704 from popcornmix/tiled_thumb

[rbp] Fix bug with CPicture::CreateTiledThumb and texture pipeline