Add a defconfig for the Allwinner Nezha, a raspberrypi-style board built
around the RISC-V 64bit D1 SoC.
There is currently no upstream support, so use the git repos from Samuel
Holland as explained on the linux-sunxi wiki:
https://linux-sunxi.org/Allwinner_Nezha
The U-Boot DTB is also used by opensbi, but the two branches are
unfortunately not in sync at the moment, so add a patch to fix the
compatible for the PLIC so opensbi makes it available to S-Mode (Linux).
The use of the sun20i-d1-spl SPL bootloader / TOC1 file format also makes it
a bit more complicated to build the boot image. As this is expected to only
be a temporary issue, add a U-Boot patch to build the TOC1 image as part of
the build rather than adding explicit support in our U-Boot package to do
it.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
