vdownmix: Add chmap support

Signed-off-by: Takashi Iwai <tiwai@suse.de>
upmix: Add chmap support

Signed-off-by: Takashi Iwai <tiwai@suse.de>
a52: Fix build error with the recent version

The version check for USE_AVCODEC_FRAME wasn't done correctly, and it
failed to build with version 54.x or later.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
a52: Add chmap support

Signed-off-by: Takashi Iwai <tiwai@suse.de>