vc4/drm: Remove the clear of SCALER_DISPBKGND_FILL

Since "drm/vc4: hvs: Support BCM2712 HVS" booting Pi4
with dual 4kp30 displays connected fails with:
vc4-drm gpu: [drm] *ERROR* [CRTC:107:pixelvalve-4] flip_done timed out

It has been tracked down to the referenced commit adding a
path to clear the SCALER_DISPBKGND_FILL when not required.

While that appears valid, it causes a problem
(that still needs to be understood).

Lets revert that change to avoid the regression for now.

Fixes: e84da23 ("drm/vc4: hvs: Support BCM2712 HVS")

Signed-off-by: Dom Cobley <[email protected]>

Author: popcornmix

drivers/gpu/drm/vc4/vc4_hvs.c

@@ -1366,10 +1366,6 @@ void vc4_hvs_atomic_flush(struct drm_crtc *crtc,
 			HVS_WRITE(SCALER6_DISPX_CTRL1(channel),
 				  HVS_READ(SCALER6_DISPX_CTRL1(channel)) &
 				  ~SCALER6_DISPX_CTRL1_BGENB);
-		else
-			HVS_WRITE(SCALER_DISPBKGNDX(channel),
-				  HVS_READ(SCALER_DISPBKGNDX(channel)) &
-				  ~SCALER_DISPBKGND_FILL);
 	}
 
 	/* Only update DISPLIST if the CRTC was already running and is not