arm64: dts: renesas: Prepare for split of ARCH_R8A7795 into ARCH_R8A7795[01]

As R-Car H3 ES1.x (R8A77950) and R-Car H3 ES2.0+ (R8A77951) are really
different SoCs, CONFIG_ARCH_R8A7795 will be split in
CONFIG_ARCH_R8A77950 and CONFIG_ARCH_R8A77951.

Relax dependencies by handling both the old and the new symbols.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/20191217183841.432-5-geert+renesas@glider.be