drm/xe/guc: s/guc_fini/guc_fini_hw/

Make it clear that is about cleaning up the HW/FW side, and not software
state.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240522102143.128069-23-matthew.auld@intel.com