demux: mp4: compute new pos for audio if blockalign is missing
demux: mp4: compute new pos for audio if blockalign is missing

Prevented playback of blockalign less audio samples

(cherry picked from commit 901cfac0e6b756cc5b0f93bf49e45666dd65d7a7)
Signed-off-by: Jean-Baptiste Kempf <7b85a41a628204b76aba4326273a3ccc74bd009a@videolan.org>

jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2