drm/msm/dsi: Remove custom DSI config handling

Now that the only user is handled by common code, remove the option to
specify custom handlers through match data.

This is effectively a revert of commit:
5ae15e76271 ("drm/msm/dsi: Allow to specify dsi config as pdata")

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/527662/
Link: https://lore.kernel.org/r/20230307-topic-dsi_qcm-v6-7-70e13b1214fa@linaro.org


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