ARM: pci: always export pcibios_bus_to_resource

Some PCI drivers call pcibios_bus_to_resource directly,
but it is only exported when CONFIG_HOTPLUG is set,
because it was initially mean for pccard support.

Moving the export out of the #ifdef lets us avoid these
build errors:

ERROR: "pcibios_bus_to_resource" [drivers/video/vt8623fb.ko] undefined!
ERROR: "pcibios_bus_to_resource" [drivers/video/arkfb.ko] undefined!
ERROR: "pcibios_bus_to_resource" [drivers/video/s3fb.ko] undefined!

Signed-off-by: Arnd Bergmann <arnd@arndb.de>