drm/msm/dpu: point sc8280xp_dpu_cfg to sc8280xp_regdma

drm/msm/dpu: point sc8280xp_dpu_cfg to sc8280xp_regdma

SC8280XP configuration missed the reg_dma configuration. We do not use
regdma for now, but let's put the correct pointer anyway.

Fixes: 4a352c2fc15a ("drm/msm/dpu: Introduce SC8280XP")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/518790/
Link: https://lore.kernel.org/r/20230118020455.1689929-1-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>