ndtest: Add dimm attributes

This patch adds sysfs attributes for nvdimm and the dimm device.

Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
Link: https://lore.kernel.org/r/20201222042240.2983755-5-santosh@fossix.org


Signed-off-by: Dan Williams <dan.j.williams@intel.com>