target/riscv/cpu.c: add riscv_cpu_add_qdev_prop_array()

target/riscv/cpu.c: add riscv_cpu_add_qdev_prop_array()

The code inside riscv_cpu_add_user_properties() became quite repetitive
after recent changes. Add a helper to hide the repetition away.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20230912132423.268494-8-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>