powerpc/powernv/npu: Check mmio_atsd array bounds when populating

A broken device tree might contain more than 8 values and introduce hard
to debug memory corruption bug. This adds the boundary check.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/powernv/npu-dma.c

@@ -1178,7 +1178,8 @@ int pnv_npu2_init(struct pci_controller *hose)
 
 	npu->nmmu_flush = of_property_read_bool(hose->dn, "ibm,nmmu-flush");
 
-	for (i = 0; !of_property_read_u64_index(hose->dn, "ibm,mmio-atsd",
+	for (i = 0; i < ARRAY_SIZE(npu->mmio_atsd_regs) &&
+			!of_property_read_u64_index(hose->dn, "ibm,mmio-atsd",
 				i, &mmio_atsd); i++)
 		npu->mmio_atsd_regs[i] = ioremap(mmio_atsd, 32);