drm/i915/dsi: Do DSC/scaler disable earlier on icl+

Do the scaler disable in the spot where bspec has specfied it
for TGL+. And also move the DSC disable to match what
intel_ddi.c does.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230608203057.23759-10-ville.syrjala@linux.intel.com