powerpc/fsl-pci: Determine pci_controller based on cfg addr for dts fixup

Previously we passed in a specifically named struct pci_controller to
determine if we had setup the particular PCI bus.  Now we can search for
the struct so we dont have to depend on the name or the struct being
statically allocated.

Introduced new find_hose_by_cfg_addr() to get back a pci_controller struct
back by searching for it means we can do things like dynamically allocate
them or not have to expose the static structures to all users.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Wolfgang Denk <wd@denx.de>