libnvdimm: remove redundant assignment to pointer 'dev'

Pointer dev is being assigned a value that is never read, it is being
re-assigned the same value later on, hence the initialization is redundant
and can be removed.

Cleans up clang warning:
drivers/nvdimm/pfn_devs.c:307:17: warning: Value stored to 'dev' during
its initialization is never read
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Reviewed-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/nvdimm/pfn_devs.c

@@ -304,7 +304,7 @@ static const struct attribute_group *nd_pfn_attribute_groups[] = {
 struct device *nd_pfn_devinit(struct nd_pfn *nd_pfn,
 		struct nd_namespace_common *ndns)
 {
-	struct device *dev = &nd_pfn->dev;
+	struct device *dev;
 
 	if (!nd_pfn)
 		return NULL;