mp3adu: Set the channel layout properly

This fixes decoding, broken since 7e35037.

This is similar to what was done for the normal mp3 decoder in
f4a86bc9.

Signed-off-by: Martin Storsjö <martin@martin.st>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  mp3adu: Set the channel layout properly

Merged-by: Michael Niedermayer <michaelni@gmx.at>
avformat/oggparseopus: Check opus_duration() return value

Regression since 39d11d599cd292485fe991cd22e10d7a1738b3bc

os->pduration would be wrongly assigned a negative value on invalid packets
instead of aborting.

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>