ARM: debug-ll: Add support for r8a7743

Enable low-level debugging support for RZ/G1M (r8a7743). RZ/G1M uses
SCIF0 for the debug console, like most of the R-Car Gen2 SoCs.

Signed-off-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>