drm: mali-dp: Don't set DRM_PLANE_COMMIT_ACTIVE_ONLY

We need to explicitly disable our planes, so don't set the flag which
would otherwise skip the plane disable when the CRTC is disabled.

Signed-off-by: Brian Starkey <brian.starkey@arm.com>
Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>