Introduces a function gred_change_vq() acting as a central point
to change VQ parameters. Fixes priority inheritance in rio mode
when the default DP equals 0. Adds proper locking during changes.
Signed-off-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NArnaldo Carvalho de Melo <acme@mandriva.com>