hw/riscv/virt: Restrict ACLINT to TCG

hw/riscv/virt: Restrict ACLINT to TCG

The Advanced Core Local Interruptor (ACLINT) device can
only be used with TCG. Check for TCG enabled instead of
KVM being not. Only add the property when TCG is used.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20230629121103.87733-3-philmd@linaro.org>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>