sh: r2dplus: Add SCIF1 to the basic DT

Add simple DT and clock bindings to r2dplus DT to permit U-Boot
to bind the SCIF driver via DT probing instead of hard-coded
config options.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>