At least on some platforms (tested on ctg) the way
vgacon does screen blanking seems to flag constant
FIFO underruns, which means we have to be prepared
for them while the driver is loading. Currently
there is a time window between drm_crtc_init() and
intel_sanitize_fifo_underrun_reporting() during
which FIFO underrun reporting is in fact marked as
enabled. Thus we may end up mistakenly detecting
these bogus underruns during driver init.

Close the race by marking FIFO underrun reporting
as disabled prior to even registering the crtc.
intel_sanitize_fifo_underrun_reporting()/etc. will
re-enable it later if needed.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230125185234.21599-2-ville.syrjala@linux.intel.comReviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>