drm/i915/guc: Fix missing ecodes

Error captures are tagged with an 'ecode'. This is a pseduo-unique magic
number that is meant to distinguish similar seeming bugs with
different underlying signatures. It is a combination of two ring state
registers. Unfortunately, the register state being used is only valid
in execlist mode. In GuC mode, the register state exists in a separate
list of arbitrary register address/value pairs rather than the named
entry structure. So, search through that list to find the two exciting
registers and copy them over to the structure's named members.

v2: if else if instead of if if (Alan)

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Fixes: a6f0f9cf ("drm/i915/guc: Plumb GuC-capture into gpu_coredump")
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Aravind Iddamsetty <aravind.iddamsetty@intel.com>
Cc: Michael Cheng <michael.cheng@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Bruce Chang <yu.bruce.chang@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230311063714.570389-2-John.C.Harrison@Intel.com