ARM: debug-ll: Add support for r8a7744

Enable low-level debugging support for RZ/G1N (R8A7744). RZ/G1N uses
SCIF0 for the debug console.

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