hw/riscv: virt: fix syscon subnode paths

hw/riscv: virt: fix syscon subnode paths

The reset and poweroff features of the syscon were originally added to
top level, which is a valid path for a syscon subnode. Subsequently a
reorganisation was carried out while implementing NUMA in which the
subnodes were moved into the /soc node. As /soc is a "simple-bus", this
path is invalid, and so dt-validate produces the following warnings:

/stuff/qemu/qemu.dtb: soc: poweroff: {'value': [[21845]], 'offset': [[0]], 'regmap': [[4]], 'compatible': ['syscon-poweroff']} should not be valid under {'type': 'object'}
        From schema: /home/conor/.local/lib/python3.9/site-packages/dtschema/schemas/simple-bus.yaml
/stuff/qemu/qemu.dtb: soc: reboot: {'value': [[30583]], 'offset': [[0]], 'regmap': [[4]], 'compatible': ['syscon-reboot']} should not be valid under {'type': 'object'}
        From schema: /home/conor/.local/lib/python3.9/site-packages/dtschema/schemas/simple-bus.yaml

Move the syscon subnodes back to the top level and silence the warnings.

Reported-by: Rob Herring <robh@kernel.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20220810184612.157317-4-mail@conchuod.ie
Link: https://lore.kernel.org/linux-riscv/20220803170552.GA2250266-robh@kernel.org/
Fixes: 18df0b4695 ("hw/riscv: virt: Allow creating multiple NUMA sockets")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>