ARM: dts: renesas: Switch to using upstream DT on Renesas R8A779H0 V4M

ARM: dts: renesas: Switch to using upstream DT on Renesas R8A779H0 V4M

Enable OF_UPSTREAM to use upstream DT and add renesas/ prefix to the
DEFAULT_DEVICE_TREE. And thereby directly build DTB from dts/upstream/src/
including *-u-boot.dtsi files from arch/$(ARCH)/dts/ directory.

This patch finalizes OF_UPSTREAM conversion of R8A779H0 V4M which DTs
landed in Linux 6.9 .

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Acked-by: Sumit Garg <sumit.garg@linaro.org>