hw/riscv/virt.c: add aplic nodename helper

hw/riscv/virt.c: add aplic nodename helper

We'll change the aplic DT nodename in the next patch and the name is
hardcoded in 2 different functions. Create a helper to change a single
place later.

While we're at it, in create_fdt_socket_aplic(), move 'aplic_name'
inside the conditional to avoid allocating a string that won't be used
when socket == NULL.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240531202759.911601-3-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>