xml: Use bitrate in constraints for AVC*
xml: Use bitrate in constraints for AVC*

This is more likely to be set than maximum-bitrate. Also, the range
starts from 1 instead of 0, to ensure that it is actually known.

luisbg/gupnp-dlna,luisbg/gupnp-dlna,GNOME/gupnp-dlna,GNOME/gupnp-dlna,GNOME/gupnp-dlna