drm/xe: Fix GT "for each engine" workarounds

drm/xe: Fix GT "for each engine" workarounds

Any rules using engine matching are currently broken due RTP processing
happening too in early init, before the list of hardware engines has been
initialised.

Fix this by moving workaround processing to later in the driver probe
sequence, to just before the processed list is used for the first time.

Looking at the debugfs gt0/workarounds on ADL-P we notice 14011060649
should be present while we see, before:

 GT Workarounds
     14011059788
     14015795083

And with the patch:

 GT Workarounds
     14011060649
     14011059788
     14015795083

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: stable@vger.kernel.org # v6.11+
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250227101304.46660-2-tvrtko.ursulin@igalia.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>