powerpc/powernv/ioda: Handle failures correctly in pnv_pci_ioda_iommu_bypass_supported()

powerpc/powernv/ioda: Handle failures correctly in pnv_pci_ioda_iommu_bypass_supported()

When the return value type was changed from int to bool, few places
were left unchanged, this fixes them. We did not hit these failures as
the first one is not happening at all and the second one is little
more likely to happen if the user switches a 33..58bit DMA capable
device between the VFIO and vendor drivers and there are not so many
of these.

Fixes: 2d6ad41b2c21 ("powerpc/powernv: use the generic iommu bypass code")
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>