libnvdimm for 4.10

* Dynamic label support: To date namespace label support has been
limited to disambiguating cases where PMEM (direct load/store) and BLK
(mmio aperture) accessed-capacity alias on the same DIMM. Since 4.9 added
support for multiple namespaces per PMEM-region there is value to
support namespace labels even in the non-aliasing case. The presence of
a valid namespace index block force-enables label support when the
kernel would otherwise rely on region boundaries, and permits the region
to be sub-divided.

* Handle media errors in namespace metadata: Complement the error
handling for media errors in namespace data areas with support for
clearing errors on writes, and downgrading potential machine-check
exceptions to simple i/o errors on read.

* Device-DAX region attributes: Add 'align', 'id', and 'size' as
attributes for device-dax regions. In particular this enables userspace
tooling to generically size memory mapping and i/o operations. Prevent
userspace from growing assumptions / dependencies about the parent
device topology for a dax region. A libnvdimm namespace may not always
be the parent device of a dax region.

* Various cleanups and small fixes.