acpi, nfit: Collect shutdown status

Some NVDIMMs, in addition to providing an indication of whether the
previous shutdown was clean, also provide a running count of lifetime
dirty-shutdown events for the device. In anticipation of this
functionality appearing on more devices arrange for the nfit driver to
retrieve / cache this data at DIMM discovery time, and export it via
sysfs.

Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>