ssb: unexport ssb_bus_pcibus_register

It isn't used anywhere out of ssb code and we don't (plan to) build
pcihost_wrapper.c as a separated module.
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/ssb/main.c

@@ -876,7 +876,6 @@ int ssb_bus_pcibus_register(struct ssb_bus *bus, struct pci_dev *host_pci)
 
 	return err;
 }
-EXPORT_SYMBOL(ssb_bus_pcibus_register);
 #endif /* CONFIG_SSB_PCIHOST */
 
 #ifdef CONFIG_SSB_PCMCIAHOST