The decoder assigns channels using default channel configuration
for 5.1ch when it parses an ADTS frame header using consecutive
channel ids.

When a PCE comes, it reassigns channels using PCE configuration
using directly the ids provided. They can be arbitrary.

Always use consecutive channel ids to avoid decoding glitches due
spurious reconfigurations due the channel ids mismatch between the
two otherwise-identical channel maps.

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>