cpu: Call object_class_dynamic_cast() once in cpu_class_by_name()

cpu: Call object_class_dynamic_cast() once in cpu_class_by_name()

For all targets, the CPU class returned from CPUClass::class_by_name()
and object_class_dynamic_cast(oc, CPU_RESOLVING_TYPE) need to be
compatible. Lets apply the check in cpu_class_by_name() for once,
instead of having the check in CPUClass::class_by_name() for individual
target.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Message-ID: <20231114235628.534334-4-gshan@redhat.com>