drm/msm/dp: Remove aux_cfg_update_done and related code

drm/msm/dp: Remove aux_cfg_update_done and related code

The member 'aux_cfg_update_done' is always false. This is dead code that
never runs. Remove it.

Cc: Vinod Polimera <quic_vpolimer@quicinc.com>
Cc: Kuogee Hsieh <quic_khsieh@quicinc.com>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Tested-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/554985/
Link: https://lore.kernel.org/r/20230829184735.2841739-5-swboyd@chromium.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>