mailbox: zynq: Switch to flexible array to simplify code

Using flexible array is more straight forward. It
  - saves 1 pointer in the 'zynqmp_ipi_pdata' structure
  - saves an indirection when using this array
  - saves some LoC and avoids some always spurious pointer arithmetic

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/zynqmp-ipi-mailbox.c

@@ -110,7 +110,7 @@ struct zynqmp_ipi_pdata {
 	unsigned int method;
 	u32 local_id;
 	int num_mboxes;
-	struct zynqmp_ipi_mbox *ipi_mboxes;
+	struct zynqmp_ipi_mbox ipi_mboxes[];
 };
 
 static struct device_driver zynqmp_ipi_mbox_driver = {
@@ -635,7 +635,7 @@ static int zynqmp_ipi_probe(struct platform_device *pdev)
 	int num_mboxes, ret = -EINVAL;
 
 	num_mboxes = of_get_child_count(np);
-	pdata = devm_kzalloc(dev, sizeof(*pdata) + (num_mboxes * sizeof(*mbox)),
+	pdata = devm_kzalloc(dev, struct_size(pdata, ipi_mboxes, num_mboxes),
 			     GFP_KERNEL);
 	if (!pdata)
 		return -ENOMEM;
@@ -649,8 +649,6 @@ static int zynqmp_ipi_probe(struct platform_device *pdev)
 	}
 
 	pdata->num_mboxes = num_mboxes;
-	pdata->ipi_mboxes = (struct zynqmp_ipi_mbox *)
-			    ((char *)pdata + sizeof(*pdata));
 
 	mbox = pdata->ipi_mboxes;
 	for_each_available_child_of_node(np, nc) {