hw/riscv/virt.c: use g_autofree in create_fdt_socket_cpus()

hw/riscv/virt.c: use g_autofree in create_fdt_socket_cpus()

Move all char pointers to the loop. Use g_autofree in all of them to
avoid the g_free() calls.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240122221529.86562-4-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>