drm/i915: stop recording IER in error capture

With pre-ilk GEN2_IER capture moved to gtier[0], the remaining IER
aren't all that relevant. Stop capturing them.

Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://lore.kernel.org/r/6f1130a3d0d13e08a73ba381225ab978b22a9345.1744630147.git.jani.nikula@intel.com


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