avcodec/decode: copy the output parameters from the last bsf in the chain back...

avcodec/decode: copy the output parameters from the last bsf in the chain back to the AVCodecContext

Certain AVCodecParameters, like the contents of the extradata, may be changed
by the init() function of any of the bitstream filters in the chain.

Signed-off-by: James Almer <jamrial@gmail.com>