libnvdimm, namespace: remove redundant initialization of 'nd_mapping'

Pointer nd_mapping is being initialized to a value that is never read,
instead it is being updated to a new value in all the cases where it
is being read afterwards, hence the initialization is redundant and
can be removed.

Cleans up clang warning:
drivers/nvdimm/namespace_devs.c:2411:21: warning: Value stored to
'nd_mapping' during its initialization is never rea
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Reviewed-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: NRoss Zwisler <ross.zwisler@linux.intel.com>

drivers/nvdimm/namespace_devs.c

@@ -2408,7 +2408,7 @@ static struct device **scan_labels(struct nd_region *nd_region)
 
 static struct device **create_namespaces(struct nd_region *nd_region)
 {
-	struct nd_mapping *nd_mapping = &nd_region->mapping[0];
+	struct nd_mapping *nd_mapping;
 	struct device **devs;
 	int i;