ARM: BCM5301X: Enable UART on Netgear R8000

It was tested by LEDE users, all we need is to adjust clock frequency.
While we're at it create a separated DTS include file to share code with
other BCM4709 devices easier.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm/boot/dts/bcm4709-asus-rt-ac87u.dts

@@ -9,7 +9,7 @@
 
 /dts-v1/;
 
-#include "bcm4708.dtsi"
+#include "bcm4709.dtsi"
 #include "bcm5301x-nand-cs0-bch8.dtsi"
 
 / {

arch/arm/boot/dts/bcm4709-buffalo-wxr-1900dhp.dts

@@ -9,7 +9,7 @@
 
 /dts-v1/;
 
-#include "bcm4708.dtsi"
+#include "bcm4709.dtsi"
 #include "bcm5301x-nand-cs0-bch8.dtsi"
 
 / {

arch/arm/boot/dts/bcm4709-netgear-r7000.dts

@@ -9,7 +9,7 @@
 
 /dts-v1/;
 
-#include "bcm4708.dtsi"
+#include "bcm4709.dtsi"
 #include "bcm5301x-nand-cs0-bch8.dtsi"
 
 / {

arch/arm/boot/dts/bcm4709-netgear-r8000.dts

@@ -9,7 +9,7 @@
 
 /dts-v1/;
 
-#include "bcm4708.dtsi"
+#include "bcm4709.dtsi"
 #include "bcm5301x-nand-cs0-bch8.dtsi"
 
 / {
@@ -107,6 +107,10 @@ restart {
 	};
 };
 
+&uart0 {
+	status = "okay";
+};
+
 &usb2 {
 	vcc-gpio = <&chipcommon 0 GPIO_ACTIVE_HIGH>;
 };

arch/arm/boot/dts/bcm4709.dtsi

+/*
+ * Copyright (C) 2016 Rafał Miłecki <rafal@milecki.pl>
+ *
+ * Licensed under the ISC license.
+ */
+
+#include "bcm4708.dtsi"
+
+&uart0 {
+	clock-frequency = <125000000>;
+};