[PATCH] yenta oops fix

In some cases, especially on modern laptops with a lot of PCI and
cardbus bridges, we're unable to assign correct secondary/subordinate
bus numbers to all cardbus bridges due to BIOS limitations unless
we are using "pci=assign-busses" boot option.
So some cardbus controllers may not have attached subordinate pci_bus
structure, and yenta driver must cope with it - just ignore such cardbus
bridges.

For example, see https://bugzilla.novell.com/show_bug.cgi?id=113778

Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>