drm/msm/dpu: remove unused dpu_plane_validate_multirect_v2 function

After cleaning up the older multirect support the function
dpu_plane_validate_multirect_v2() is unused. Lets remove it.

Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
[DB: also drop struct dpu_multirect_plane_states and R0/R1/R_MAX]
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/527348/
Link: https://lore.kernel.org/r/20230316161653.4106395-33-dmitry.baryshkov@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>