acpi, nfit: Prefer _DSM over _LSR for namespace label reads

The _LSR method indicates locked status via error-code-3 returned in the
_LSR payload. When any error is returned the payload of _LSR is
truncated to a zero-length buffer.

The _DSM path in comparison allows system software to retrieve the
locked status *and* namespace label area contents.

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