MFC r344474-r344476

r344474:
nvdimm: split spa dev into a separate entity

Separate code for exposing a device backed by a system physical
address range away from the NVDIMM spa code. This will allow a
future patch to add support for NVDIMM namespaces while using the
same device code.

Submitted by: D Scott Phillips <d.scott.phillips@intel.com>
Reviewed by: bwidawsk
Sponsored by: Intel Corporation
Differential Revision: https://reviews.freebsd.org/D18736

r344475:
nvdimm: Read NVDIMM namespace labels

When attaching to NVDIMM devices, read and verify the namespace
labels from the special namespace label storage area. A later
change will expose NVDIMM namespaces derived from this label data.

Submitted by: D Scott Phillips <d.scott.phillips@intel.com>
Discussed with: kib
Sponsored by: Intel Corporation
Differential Revision: https://reviews.freebsd.org/D18735

r344476:
nvdimm: Simple namespace support

Add support for simple NVDIMM v1.2 namespaces from the UEFI
version 2.7 specification. The combination of NVDIMM regions and
labels can lead to a wide variety of namespace layouts. Here we
support a simple subset of namespaces where each NVDIMM SPA range
is composed of a single region per member dimm.

Submitted by: D Scott Phillips <d.scott.phillips@intel.com>
Discussed with: kib
Sponsored by: Intel Corporation
Differential Revision: https://reviews.freebsd.org/D18736