accel: add init_accel_cpu for adapting accel behavior to CPU type

accel: add init_accel_cpu for adapting accel behavior to CPU type

while on x86 all CPU classes can use the same set of TCGCPUOps,
on ARM the right accel behavior depends on the type of the CPU.

So we need a way to specialize the accel behavior according to
the CPU. Therefore, add a second initialization, after the
accel_cpu->cpu_class_init, that allows to do this.

Signed-off-by: Claudio Fontana <cfontana@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210322132800.7470-24-cfontana@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>