drm/i915/reset: Disable execlist per-engine reset for display reset tests

drm/i915/reset: Disable execlist per-engine reset for display reset tests

The display reset only happens from the full reset path. We must
therefore force execlist submission to always take the full reset
path and not the per-engine reset path. Currently the display
reset tests are in fact not testing display resets at all on
platforms using execlist submission. Ring submission and GuC
submission always take the full path anyway.

Also disable the engine reset inside __intel_gt_set_wedged() so
that we simulate the intel_gt_gpu_reset_clobbers_display() behavior
as closely as possible also when taking the full wedge path.

The slight race between the separate intel_display_reset_test()
calls in the overall reset path is harmless. kms_busy will keep
the modparam fixed during the test, and even if someone were to
fiddle with the modparam manually nothing bad should happen if
the calls return different values.

Cc: Jouni Högander <jouni.hogander@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260415210411.24750-8-ville.syrjala@linux.intel.com