hw/riscv/virt.c: use g_autofree in create_fdt_*

hw/riscv/virt.c: use g_autofree in create_fdt_*

We have a lot of cases where a char or an uint32_t pointer is used once
to alloc a string/array, read/written during the function, and then
g_free() at the end. There's no pointer re-use - a single alloc, a
single g_free().

Use 'g_autofree' to avoid the g_free() calls.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240122221529.86562-8-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>