target/riscv: Remove AccelCPUClass::cpu_class_init need

target/riscv: Remove AccelCPUClass::cpu_class_init need

Expose riscv_tcg_ops symbol, then directly set it as
CPUClass::tcg_ops in TYPE_RISCV_CPU's class_init(),
using CONFIG_TCG #ifdef'ry. No need for the
AccelCPUClass::cpu_class_init() handler anymore.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250405161320.76854-2-philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>