drm/msm/dsi: split dsi_ctrl_config() function

It makes no sense to pass NULL parameters to dsi_ctrl_config() in the
disable case. Split dsi_ctrl_config() into enable and disable parts and
drop unused params.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Patchwork: https://patchwork.freedesktop.org/patch/542559/
Link: https://lore.kernel.org/r/20230614224402.296825-2-dmitry.baryshkov@linaro.org