drm/msm/dpu: rip out master planes support

Master/virtual planes were used for multirect support. In preparation to
reworking DPU planes, drop support for master planes (which was not used
anyway).

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/473146/
Link: https://lore.kernel.org/r/20220209172520.3719906-2-dmitry.baryshkov@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>