powerpc/fsl-pci: Add generic code to setup PCIe controllers

Since all the PCIe controllers are connected over SERDES on the SoCs we
can utilize is_serdes_configured() to determine if a controller is
enabled.  After which we can setup the ATMUs and LAWs for the controller
in a common fashion and allow board code to specify what the controller
is connected to for reporting reasons.

We also provide a per controller (rather than all) for some systems that
may have special requirements.

Finally, we refactor the code used by the P1022DS to utilize the new
generic code.

Based on patch by: Li Yang <leoli@freescale.com>

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>