drm/i915/mst: Swap TRANSCONF vs. FECSTALL_DIS_DPTSTREAM_DPTTG disable

The DP modeset sequence asks us to disable TRANSCONF before clearing
the FECSTALL_DIS_DPTSTREAM_DPTTG bit, although we are still asked
to wait for the transcoder to stop only after both steps have
been done.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231018154123.5479-2-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>