drm/radeon/kms: rework audio polling timer

Rework HDMI audio polling timer, only enable it when
at least one HDMI encoder needs it. Preparation for
replacing it with irq support.

Signed-off-by: Christian König <deathsimple@vodafone.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
4 files changed