powerpc/pci: remove duplicate declaration of pci_bus_find_capability

pci_bus_find_capability() is decleared in pci.h, so it is not necessary to do
it again.

This patch removes it.
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>

arch/powerpc/kernel/pci-common.c

@@ -1561,7 +1561,6 @@ EARLY_PCI_OP(write, byte, u8)
 EARLY_PCI_OP(write, word, u16)
 EARLY_PCI_OP(write, dword, u32)
 
-extern int pci_bus_find_capability (struct pci_bus *bus, unsigned int devfn, int cap);
 int early_find_capability(struct pci_controller *hose, int bus, int devfn,
 			  int cap)
 {