Enable PCIe controller nodes to enable respective PCIe slots on
P2972-0000 board. Following is the ownership of slots by different
PCIe controllers.
Controller-0 : M.2 Key-M slot
Controller-1 : On-board Marvell eSATA controller
Controller-3 : M.2 Key-E slot
Signed-off-by: NVidya Sagar <vidyas@nvidia.com>
Signed-off-by: NThierry Reding <treding@nvidia.com>