Allow vpxdec to produce target tile reconstruction

Allow vpxdec to produce target tile reconstruction

This commit allows the vpxdec to produce the target tile
reconstruction as its output. When the provided tile index is -1,
the entire corresponding row/column tiles will be reconstructed.
If the tile index is over the upper limit, the decoder will decode
left-most/bottom tile.

Change-Id: I4c18bdb32099f736f99b8842f7f177a32b3fee09