drm/msm/dpu: bind correct pingpong for quad pipe

drm/msm/dpu: bind correct pingpong for quad pipe

There are 2 interfaces and 4 pingpong in quad pipe. Map the 2nd
interface to 3rd PP instead of the 2nd PP.

Signed-off-by: Jun Nie <jun.nie@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/675402/
Link: https://lore.kernel.org/r/20250918-v6-16-rc2-quad-pipe-upstream-4-v16-2-ff6232e3472f@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>