pci_dn->phb is set to phb in update_dn_pci_info(), if succeed.

This patch removes the duplication of pci_dn->phb initialization.
Signed-off-by: NWei Yang <weiyang@linux.vnet.ibm.com>
Reviewed-by: NGavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>