aaccoder: remove previous PNS implementation from twoloop

This commit undoes commit c5d4f87e
and removes PNS band marking from the twoloop coder, which has
been reimplemented in a better way in this series of patches.

Reviewed-by: Claudio Freire <klaussfreire@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>