kvm: reset state from the CPU's reset method

kvm: reset state from the CPU's reset method

Now that we have a CPU object with a reset method, it is better to
keep the KVM reset close to the CPU reset.  Using qemu_register_reset
as we do now keeps them far apart.

With this patch, PPC no longer calls the kvm_arch_ function, so
it can get removed there.  Other arches call it from their CPU
reset handler, and the function gets an ARMCPU/X86CPU/S390CPU.

Note that ARM- and s390-specific functions are called kvm_arm_*
and kvm_s390_*, while x86-specific functions are called kvm_arch_*.
That follows the convention used by the different architectures.
Changing that is the topic of a separate patch.

Reviewed-by: Gleb Natapov <gnatapov@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>