i386: run accel_cpu_instance_init as post_init

i386: run accel_cpu_instance_init as post_init

This fixes host and max cpu initialization, by running the accel cpu
initialization only after all instance init functions are called for all
X86 cpu subclasses.

The bug this is fixing is related to the "max" and "host" i386 cpu
subclasses, which set cpu->max_features, which is then used at cpu
realization time.

In order to properly split the accel-specific max features code that
needs to be executed at cpu instance initialization time,

we cannot call the accel cpu initialization at the end of the x86 base
class initialization, or we will have no way to specialize
"max features" cpu behavior, overriding the "max" cpu class defaults,
and checking for the "max features" flag itself.

This patch moves the accel-specific cpu instance initialization to after
all x86 cpu instance code has been executed, including subclasses,

so that proper initialization of cpu "host" and "max" can be restored.

Fixes: f5cc5a5c ("i386: split cpu accelerators from cpu.c,"...)
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Claudio Fontana <cfontana@suse.de>
Message-Id: <20210603123001.17843-3-cfontana@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>