powerpc: Drop superfluous pci_dev_is_added() calls

On powerpc, pci_dev_is_added() is called as part of SR-IOV fixups
that are done under pcibios_add_device() which in turn is only called in
pci_device_add() whih is called when a PCI device is scanned.

pci_dev_assign_added() is called in pci_bus_add_device() which is only
called after scanning the device. Thus pci_dev_is_added() is always
false and can be dropped.

Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Oliver O'Halloran <oohall@gmail.com>
[mpe: Tweak change log slightly to reflect Oliver's comments]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210910141940.2598035-2-schnelle@linux.ibm.com