pinctrl: st: fix leaked of_node references

The call to of_get_child_by_name returns a node pointer with refcount
incremented thus it must be explicitly decremented after the last
usage.

Detected by coccinelle with the following warnings:
./drivers/pinctrl/pinctrl-st.c:1188:3-9: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 1175, but without a corresponding object release within this function.
./drivers/pinctrl/pinctrl-st.c:1188:3-9: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 1175, but without a corresponding object release within this function.
./drivers/pinctrl/pinctrl-st.c:1199:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 1175, but without a corresponding object release within this function.
./drivers/pinctrl/pinctrl-st.c:1199:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 1175, but without a corresponding object release within this function.

Signed-off-by: Wen Yang <[e-mail]>
Cc: Patrice Chotard <[e-mail]>
Cc: Linus Walleij <[e-mail]>
Cc: [e-mail]
Cc: [e-mail] (open list)
Reviewed-by: Patrice Chotard <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/pinctrl/pinctrl-st.c

···
 	struct property *pp;
 	struct st_pinconf *conf;
 	struct device_node *pins;
-	int i = 0, npins = 0, nr_props;
+	int i = 0, npins = 0, nr_props, ret = 0;
 
 	pins = of_get_child_by_name(np, "st,pins");
 	if (!pins)
···
 			npins++;
 		} else {
 			pr_warn("Invalid st,pins in %pOFn node\n", np);
-			return -EINVAL;
+			ret = -EINVAL;
+			goto out_put_node;
 		}
 	}
 
···
 	grp->pin_conf = devm_kcalloc(info->dev,
 					npins, sizeof(*conf), GFP_KERNEL);
 
-	if (!grp->pins || !grp->pin_conf)
-		return -ENOMEM;
+	if (!grp->pins || !grp->pin_conf) {
+		ret = -ENOMEM;
+		goto out_put_node;
+	}
 
 	/* <bank offset mux direction rt_type rt_delay rt_clk> */
 	for_each_property_of_node(pins, pp) {
···
 		}
 		i++;
 	}
+
+out_put_node:
 	of_node_put(pins);
 
-	return 0;
+	return ret;
 }
 
 static int st_pctl_parse_functions(struct device_node *np,