UPSTREAM: libnvdimm/of_pmem: Provide a unique name for bus provider

ndctl binaries, v66 and older, mistakenly require the ndbus to have
unique names. If not while enumerating the bus in userspace it drops bus
with similar names.  This results in us not listing devices beneath the
bus.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Tested-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Link: https://lore.kernel.org/r/20190807040029.11344-1-aneesh.kumar@linux.ibm.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>
(cherry picked from commit 49bddc73d15c25a68e4294d76fc74519fda984cd)
Bug: 146400078
Bug: 148297388
Change-Id: Ieda4557bbda63e554e2eda6b87d7ba2a6e149e3b
Signed-off-by: Alistair Delva <adelva@google.com>