firmware: arm_scmi: fix of_node leak in scmi_mailbox_check

of_parse_phandle_with_args() requires the caller to call of_node_put() on
the returned args->np pointer. Otherwise the reference count will remain
incremented.

However, in this case, since we don't actually use the returned pointer,
we can simply pass in NULL.

Fixes: aa4f886f ("firmware: arm_scmi: add basic driver infrastructure for SCMI")
Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/driver.c

@@ -654,9 +654,7 @@ static int scmi_xfer_info_init(struct scmi_info *sinfo)
 
 static int scmi_mailbox_check(struct device_node *np)
 {
-	struct of_phandle_args arg;
-
-	return of_parse_phandle_with_args(np, "mboxes", "#mbox-cells", 0, &arg);
+	return of_parse_phandle_with_args(np, "mboxes", "#mbox-cells", 0, NULL);
 }
 
 static int scmi_mbox_free_channel(int id, void *p, void *data)