ARM: debug-ll: Add support for r8a7745

Enable low-level debugging support for RZ/G1E (r8a7745). RZ/G1E uses
SCIF4 for the debug console.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Chris Paterson <chris.paterson2@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>