powerpc/powernv/pci: Adapt is_pnv_opal_msi() to detect passthrough interrupt

The pnv_ioda2_msi_eoi() chip handler is not used anymore for MSIs.
Simply use the check on the PSI-MSI chip.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210701132750.1475580-27-clg@kaod.org