drm/i915: Sanitize underrun reporting before turning off any pipes

Make sure FIFO underrun reporting is flagged as disabled very
early during the state readout so that we don't get any
spurious FIFO underruns reports from intel_crtc_disable_noatomic().

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220615174851.20658-2-ville.syrjala@linux.intel.com


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