powerpc/fsl: update compatiable on fsl 16550 uart nodes

The Freescale serial port's are pretty much a 16550, however there are
some FSL specific bugs and features.  Add a "fsl,ns16550" compatiable
string to allow code to handle those FSL specific issues.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/boot/dts/fsl/pq3-duart-0.dtsi

@@ -35,7 +35,7 @@
 serial0: serial@4500 {
 	cell-index = <0>;
 	device_type = "serial";
-	compatible = "ns16550";
+	compatible = "fsl,ns16550", "ns16550";
 	reg = <0x4500 0x100>;
 	clock-frequency = <0>;
 	interrupts = <42 2 0 0>;
@@ -44,7 +44,7 @@ serial0: serial@4500 {
 serial1: serial@4600 {
 	cell-index = <1>;
 	device_type = "serial";
-	compatible = "ns16550";
+	compatible = "fsl,ns16550", "ns16550";
 	reg = <0x4600 0x100>;
 	clock-frequency = <0>;
 	interrupts = <42 2 0 0>;

arch/powerpc/boot/dts/fsl/qoriq-duart-0.dtsi

@@ -35,7 +35,7 @@
 serial0: serial@11c500 {
 	cell-index = <0>;
 	device_type = "serial";
-	compatible = "ns16550";
+	compatible = "fsl,ns16550", "ns16550";
 	reg = <0x11c500 0x100>;
 	clock-frequency = <0>;
 	interrupts = <36 2 0 0>;
@@ -44,7 +44,7 @@ serial0: serial@11c500 {
 serial1: serial@11c600 {
 	cell-index = <1>;
 	device_type = "serial";
-	compatible = "ns16550";
+	compatible = "fsl,ns16550", "ns16550";
 	reg = <0x11c600 0x100>;
 	clock-frequency = <0>;
 	interrupts = <36 2 0 0>;

arch/powerpc/boot/dts/fsl/qoriq-duart-1.dtsi

@@ -35,7 +35,7 @@
 serial2: serial@11d500 {
 	cell-index = <2>;
 	device_type = "serial";
-	compatible = "ns16550";
+	compatible = "fsl,ns16550", "ns16550";
 	reg = <0x11d500 0x100>;
 	clock-frequency = <0>;
 	interrupts = <37 2 0 0>;
@@ -44,7 +44,7 @@ serial2: serial@11d500 {
 serial3: serial@11d600 {
 	cell-index = <3>;
 	device_type = "serial";
-	compatible = "ns16550";
+	compatible = "fsl,ns16550", "ns16550";
 	reg = <0x11d600 0x100>;
 	clock-frequency = <0>;
 	interrupts = <37 2 0 0>;