drm/i915/guc: Consolidate duplicated capture list code

Remove 99% duplicated steered register list code. Also, include the
pre-Xe steered registers in the pre-Xe list generation.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230428185636.457407-3-John.C.Harrison@Intel.com