hw/riscv/virt: Use setprop_sized_cells for memory

hw/riscv/virt: Use setprop_sized_cells for memory

Use qemu_fdt_setprop_sized_cells to do the job of splitting the upper
and lower 32 bits across cells.

Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>
Message-ID: <20250604025450.85327-4-joel@jms.id.au>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>