ARM: iop13xx: mark iop13xx_scan_bus as __devinit

pci_scan_root_bus is __devinit, so iop13xx_scan_bus has to be the
same in order to safely call it. This is ok because the function
itself is only called from the hwpci->scan callback.

WARNING: vmlinux.o(.text+0x10138): Section mismatch in reference from the function iop13xx_scan_bus() to the function .devinit.text:pci_scan_root_bus()
The function iop13xx_scan_bus() references
the function __devinit pci_scan_root_bus().
This is often because iop13xx_scan_bus lacks a __devinit
annotation or the annotation of pci_scan_root_bus is wrong.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Lennert Buytenhek <kernel@wantstofly.org>
Cc: Dan Williams <djbw@fb.com>