ARM: dts: NSP: Add Ax stepping modifications

While uncommon, some Ax NSP SoCs exist in the wild. This stepping
requires a modified secondary CPU boot-reg and removal of DMA coherency
properties. Without these modifications, the secondary CPU will be
inactive and many peripherals will exhibit undefined behaviour.

Signed-off-by: Matthew Hagan <mnhagan88@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm/boot/dts/bcm-nsp-ax.dtsi

@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
+/*
+ * Broadcom Northstar Plus Ax stepping-specific bindings.
+ * Notable differences from B0+ are the secondary-boot-reg and
+ * lack of DMA coherency.
+ */
+
+&cpu1 {
+	secondary-boot-reg = <0xffff042c>;
+};
+
+&dma {
+	/delete-property/ dma-coherent;
+};
+
+&sdio {
+	/delete-property/ dma-coherent;
+};
+
+&amac0 {
+	/delete-property/ dma-coherent;
+};
+
+&amac1 {
+	/delete-property/ dma-coherent;
+};
+
+&amac2 {
+	/delete-property/ dma-coherent;
+};
+
+&ehci0 {
+	/delete-property/ dma-coherent;
+};
+
+&mailbox {
+	/delete-property/ dma-coherent;
+};
+
+&xhci {
+	/delete-property/ dma-coherent;
+};
+
+&ehci0 {
+	/delete-property/ dma-coherent;
+};
+
+&ohci0 {
+	/delete-property/ dma-coherent;
+};
+
+&i2c0 {
+	/delete-property/ dma-coherent;
+};
+
+&sata {
+	/delete-property/ dma-coherent;
+};
+
+&pcie0 {
+	/delete-property/ dma-coherent;
+};
+
+&pcie1 {
+	/delete-property/ dma-coherent;
+};
+
+&pcie2 {
+	/delete-property/ dma-coherent;
+};