microblaze/PCI: Remove unused declarations

The following declarations were copied from powerpc but are unused on
microblaze:

  struct pci_controller *init_phb_dynamic(struct device_node *dn)
  int remove_phb_dynamic(struct pci_controller *phb)
  struct pci_dev *of_create_pci_dev(struct device_node *node, ...)
  void of_scan_pci_bridge(struct device_node *node, ...)
  void of_scan_bus(struct device_node *node, struct pci_bus *bus)
  void of_rescan_bus(struct device_node *node, struct pci_bus *bus)

Remove them.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Michal Simek <monstr@monstr.eu>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>