[media] Remove Annex A/C selection via roll-off factor

Instead of using a roll-off factor, change DRX-K & friends to select
the bandwidth filter and the Nyquist half roll-off via delivery system.

This provides a cleaner support for Annex A/C switch.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>