RISC-V Devicetree fixes for v6.8-final

Starfive:
The previous cleanup broke boot on the jh7100 as the driver depended on
the fallback clock name created based on the node-name when
clock-output-names is not present. Add clock-output-names to restore
working order.

Generic:
BUILTIN_DTB has been broken for ages on any platform other than the
nommu Canaan k210 SoC as the first dtb built (in alphanumerical order),
would get built into the image. This didn't get fixed for ages because
nobody actually cared about running it other than the k210 enough to
fix it. The folks doing Sophgo SG2042 development have come along and
fixed it, as they want to use builtin dtbs. linux-boot on that platform
reuses the dtb it was provided by OpenSBI when booting linux proper,
which is unfortunately not possible to boot a mainline kernel with.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
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