hw/core/machine: Fix -machine dumpdtb=file.dtb

hw/core/machine: Fix -machine dumpdtb=file.dtb

In commit 8fd2518ef2f8 ("hw: Centralize handling of -machine dumpdtb
option") the call to dump was moved with respect to the init of the
machine.  This resulted in the device tree missing parts of the machine
description, depending on how they construct their device tree.

The arm virt machine is missing some PSCI nodes, while the riscv one
is missing most of its content.

Move the dump to after the notifiers have been run, allowing
virt_machine_done to be called and the device tree to be fully
populated.

Fixes: 8fd2518ef2f8 ("hw: Centralize handling of -machine dumpdtb option")
Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250401041509.719153-1-joel@jms.id.au>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>