mailbox: zynqmp-ipi: Fix out-of-bounds access in mailbox cleanup loop

The cleanup loop was starting at the wrong array index, causing
out-of-bounds access.
Start the loop at the correct index for zero-indexed arrays to prevent
accessing memory beyond the allocated array bounds.

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

@@ -890,7 +890,7 @@ static void zynqmp_ipi_free_mboxes(struct zynqmp_ipi_pdata *pdata)
 	if (pdata->irq < MAX_SGI)
 		xlnx_mbox_cleanup_sgi(pdata);
 
-	i = pdata->num_mboxes;
+	i = pdata->num_mboxes - 1;
 	for (; i >= 0; i--) {
 		ipi_mbox = &pdata->ipi_mboxes[i];
 		if (device_is_registered(&ipi_mbox->dev))