drm/i915/guc: Only assign guc_id.id when stealing guc_id

Previously assigned whole guc_id structure (list, spin lock) which is
incorrect, only assign the guc_id.id.

Fixes: 0f797650 ("drm/i915/guc: Rework and simplify locking")
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211214170500.28569-3-matthew.brost@intel.com