hw/openrisc: Support monitor dumpdtb command

The openrisc machines don't set MachineState::fdt to point to their
DTB blob.  This means that although the command line '-machine
dumpdtb=file.dtb' option works, the equivalent QMP and HMP monitor
commands do not, but instead produce the error "This machine doesn't
have a FDT".

Set MachineState::fdt in openrisc_load_fdt(), when we write it to
guest memory.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20250206151214.2947842-3-peter.maydell@linaro.org

hw/openrisc/virt.c

@@ -540,7 +540,7 @@ static void openrisc_virt_init(MachineState *machine)
                                              machine->initrd_filename,
                                              load_addr, machine->ram_size);
         }
-        boot_info.fdt_addr = openrisc_load_fdt(state->fdt, load_addr,
+        boot_info.fdt_addr = openrisc_load_fdt(machine, state->fdt, load_addr,
                                                machine->ram_size);
     }
 }