KVM: async_pf: Add missing call for async page present

Commit KVM: async_pf: Provide additional direct page notification
missed the call from kvm_check_async_pf_completion to the new introduced function.

Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>