drm/i915: add audio power domain

This way the code is simpler and can also be used for other platforms
where the audio power domain->power well mapping is different.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Paulo Zanoni <paulo.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 18ff544..4ef8e81 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -113,6 +113,7 @@
 	POWER_DOMAIN_TRANSCODER_C,
 	POWER_DOMAIN_TRANSCODER_EDP,
 	POWER_DOMAIN_VGA,
+	POWER_DOMAIN_AUDIO,
 	POWER_DOMAIN_INIT,
 
 	POWER_DOMAIN_NUM,