drm/msm/dpu: Remove an unused enum

enum dpu_ad isn't used and can be safely removed.
Reviewed-by: Jeykumar Sankaran <jsanka@codeaurora.org>
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h

@@ -232,12 +232,6 @@ enum dpu_wb {
 	WB_MAX
 };
 
-enum dpu_ad {
-	AD_0 = 0x1,
-	AD_1,
-	AD_MAX
-};
-
 enum dpu_cwb {
 	CWB_0 = 0x1,
 	CWB_1,