KVM: s390: Push run loop into __vcpu_run

Moved the do-while loop from kvm_arch_vcpu_ioctl_run into __vcpu_run
and the calling of kvm_handle_sie_intercept() into vcpu_post_run()
(so we can add the srcu locks in a proper way in the next patch).

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>