PCI: fix section mismatch warning in pci_scan_child_bus

Fix following warning:
WARNING: vmlinux.o(.text+0x47bdb1): Section mismatch in reference from the function pci_scan_child_bus() to the function .devinit.text:pcibios_fixup_bus()

We had plenty of functions that could be annotated __devinit but due to
the former restriction that exported symbols could not be annotated
they were not so.  So annotate these function and fix the references
from the pci/hotplug/* code to silence the resuting warnings.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>