drm/i915/dsi: Move panel reset+power off to be the last thing

Follow what Windows does and do the DSI panel reset+power off
after everything else.

v2: s/intel_dsi_msleep/msleep/

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/20230608203057.23759-12-ville.syrjala@linux.intel.com