KVM: e500: always restore irqs

If find_linux_pte fails, IRQs will not be restored.  This is unlikely
to happen in practice since it would have been reported as hanging
hosts, but it should of course be fixed anyway.

Cc: stable@vger.kernel.org
Reported-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>