drm/i915: Kill the leftover RMW from ivb_sprite_disable()

We still had one lingering RMW in ivb_sprite_disable(), all the other
RMWs were killed off from the sprite code some time ago. Kill the
straggler too.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_sprite.c

@@ -613,7 +613,7 @@ ivb_disable_plane(struct drm_plane *plane, struct drm_crtc *crtc)
 	struct intel_plane *intel_plane = to_intel_plane(plane);
 	int pipe = intel_plane->pipe;
 
-	I915_WRITE(SPRCTL(pipe), I915_READ(SPRCTL(pipe)) & ~SPRITE_ENABLE);
+	I915_WRITE(SPRCTL(pipe), 0);
 	/* Can't leave the scaler enabled... */
 	if (intel_plane->can_scale)
 		I915_WRITE(SPRSCALE(pipe), 0);