ARM: debug-ll: Add support for r8a77470

Enable low-level debugging support for RZ/G1C (r8a77470). RZ/G1C uses
SCIF1 for the debug console.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>