UPSTREAM: libnvdimm: Add device-tree based driver

This patch adds peliminary device-tree bindings for persistent memory
regions. The driver registers a libnvdimm bus for each pmem-region
node and each address range under the node is converted to a region
within that bus.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
(cherry picked from commit 7171976089528cb3d057a6fb288e7f8f89ab7f68)
Bug: 146400078
Bug: 148297388
Change-Id: I1dc76c36adecd82c2e9a248c8012c7b31c146cd7
Signed-off-by: Alistair Delva <adelva@google.com>