drm/msm/dpu: drop the regdma configuration

drm/msm/dpu: drop the regdma configuration

The regdma is currently not used by the current driver. We have no way
to practically verify that the regdma is described correctly. Drop it
now.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/533148/
Link: https://lore.kernel.org/r/20230420222558.1208887-1-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>