powerpc/pci: Use pci_is_pcie() to simplify code

Use pci_is_pcie() to simplify code.

Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Reviewed-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Cc: Gavin Shan <shangw@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>