vpu: decoder: fixed memory leak in fallback mode buffers
vpu: decoder: fixed memory leak in fallback mode buffers

Even though the memory is freed when the pipeline finishes, it was building
up lots of no longer used but still allocated memory blocks
Now, blocks that are no longer used get removed (and deallocated)
immediately

Signed-off-by: Carlos Rafael Giani <d7d2e6b3863b2910d2ca34828bc651c85d88df6f@pseudoterminal.org>

commshare/gstreamer-imx,Josuercuevas/gstreamer-imx,commshare/gstreamer-imx,Josuercuevas/gstreamer-imx