arm64: dts: renesas: Factor out Draak board support

Move the common parts for the Renesas Draak board to draak.dtsi, to
avoid future duplication of board descriptions.

Change a reference in a comment from "r8a77995" to "R-Car D3(e)", to
prepare for the advent of "R-Car D3e".
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/32618abb48004793f2e030d29b3a038edc05f136.1628766192.git.geert+renesas@glider.be