Add the Microsoft _DSM command set to the white list of NVDIMM command
sets.

This command set is documented at:

    https://msdn.microsoft.com/library/windows/hardware/mt604741

Cc: Pavel Machek <pavel@ucw.cz>
[pavel: fix up braces]
Signed-off-by: Stuart Hayes <stuart.w.hayes@gmail.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>