crypto: nx - add missing call to of_node_put()

In one of the error paths of the for_each_child_of_node() loop,
add missing call to of_node_put().

Fix the following coccicheck warning:
./drivers/crypto/nx/nx-common-powernv.c:927:1-23: WARNING: Function
"for_each_child_of_node" should have of_node_put() before return around
line 936.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/nx/nx-common-powernv.c

@@ -932,8 +932,10 @@ static int __init nx_powernv_probe_vas(struct device_node *pn)
 			ret = find_nx_device_tree(dn, chip_id, vasid,
 				NX_CT_GZIP, "ibm,p9-nx-gzip", &ct_gzip);
 
-		if (ret)
+		if (ret) {
+			of_node_put(dn);
 			return ret;
+		}
 	}
 
 	if (!ct_842 || !ct_gzip) {