powerpc/85xx: Rework MPC8536DS device trees

Utilize new split between board & SoC, and new SoC device trees split
into pre & post utilizing 'template' includes for SoC IP blocks.

Other changes include:
* Moved to specifying interrupt-parent for mpic at root
* Moved to 4-cell mpic interrupt cells to support MPIC timers
* Added localbus node, but no chipselect details at this point
* Reworked PCIe nodes to allow supportin IRQs for controller (errors)
* and moved
  PCI device IRQs down to virtual bridge level
* Moved mdio nodes up one level instead of under tsec nodes
* Added GPIO controller node to MPC8536 SoC template
  [ marked as MPC8572 compatiable to get errata handling that applies ]
* Added missing cache-line-size & cache-size properties missing from
  L2-cache node
* Added IP level IEEE 1588 / ptp timer node

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