powerpc/t4240: fix per pci endpoint liodn offsets

Update the code that builds the pci endpoint liodn
offset list so that it doesn't overlap with other
liodns and doesn't generate negative offsets like:

  fsl,liodn-offset-list = <0 0xffffffcd 0xffffffcf
                             0xffffffd1 0xffffffd3
                             0xffffffd5 0xffffffd7
                             0xffffffd9 0xffffffdb>;

The update consists in adding a parameter to the
function that builds the list to specify the base
liodn.
On PCI v2.4 use the old base = 256 and, on PCI 3.0
where some of the PCIE liodns are larger than 256,
use a base = 1024. The version check is based on
the PCI controller's version register.

Signed-off-by: Laurentiu Tudor <Laurentiu.Tudor@freescale.com>
Cc: Scott Wood <scottwood@freescale.com>
Cc: York Sun <yorksun@freescale.com>