drm/msm/dpu: Disable dither in phys encoder cleanup

Disable pingpong dither in dpu_encoder_helper_phys_cleanup().

This avoids the issue where an encoder unknowingly uses dither after
reserving a pingpong block that was previously bound to an encoder that
had enabled dither.

Cc: stable@vger.kernel.org
Reported-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Closes: https://lore.kernel.org/all/jr7zbj5w7iq4apg3gofuvcwf4r2swzqjk7sshwcdjll4mn6ctt@l2n3qfpujg3q/


Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Fixes: 3c128638 ("drm/msm/dpu: add support for dither block in display")
Patchwork: https://patchwork.freedesktop.org/patch/636517/
Link: https://lore.kernel.org/r/20250211-dither-disable-v1-1-ac2cb455f6b9@quicinc.com


Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>