acpi, nfit: Show bus_dsm_mask in sysfs

Display bus_dsm_mask in sysfs as /sys/bus/nd/devices/ndbusX/nfit/dsm_mask.
Signed-off-by: NJerry Hoemann <jerry.hoemann@hpe.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/acpi/nfit/core.c

@@ -929,6 +929,17 @@ static int nfit_mem_init(struct acpi_nfit_desc *acpi_desc)
 	return 0;
 }
 
+static ssize_t bus_dsm_mask_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct nvdimm_bus *nvdimm_bus = to_nvdimm_bus(dev);
+	struct nvdimm_bus_descriptor *nd_desc = to_nd_desc(nvdimm_bus);
+
+	return sprintf(buf, "%#lx\n", nd_desc->bus_dsm_mask);
+}
+static struct device_attribute dev_attr_bus_dsm_mask =
+		__ATTR(dsm_mask, 0444, bus_dsm_mask_show, NULL);
+
 static ssize_t revision_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
@@ -1065,6 +1076,7 @@ static struct attribute *acpi_nfit_attributes[] = {
 	&dev_attr_revision.attr,
 	&dev_attr_scrub.attr,
 	&dev_attr_hw_error_scrub.attr,
+	&dev_attr_bus_dsm_mask.attr,
 	NULL,
 };