intel/fs: Lower 64-bit MOVs after lower_load_payload()

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
(cherry picked from commit c06ba835)

Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3130>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3130>