mailbox: zynqmp-ipi: Remove dev.parent check in zynqmp_ipi_free_mboxes

The ipi_mbox->dev.parent check is unreliable proxy for registration
status as it fails to protect against probe failures that occur after
the parent is assigned but before device_register() completes.

device_is_registered() is the canonical and robust method to verify the
registration status.

Remove ipi_mbox->dev.parent check in zynqmp_ipi_free_mboxes().

Fixes: 4981b82 ("mailbox: ZynqMP IPI mailbox controller")
Signed-off-by: Harini T <harini.t@amd.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

Author: Harini T

drivers/mailbox/zynqmp-ipi-mailbox.c

@@ -893,10 +893,8 @@ static void zynqmp_ipi_free_mboxes(struct zynqmp_ipi_pdata *pdata)
 	i = pdata->num_mboxes;
 	for (; i >= 0; i--) {
 		ipi_mbox = &pdata->ipi_mboxes[i];
-		if (ipi_mbox->dev.parent) {
-			if (device_is_registered(&ipi_mbox->dev))
-				device_unregister(&ipi_mbox->dev);
-		}
+		if (device_is_registered(&ipi_mbox->dev))
+			device_unregister(&ipi_mbox->dev);
 	}
 }