The existing code programmed TVT#0 with some address and then
immediately released that memory.

This makes use of pnv_pci_ioda2_unset_window() and
pnv_pci_ioda2_set_bypass() which do correct resource release and
TVT update.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>