arm: dts: marvell: clearfog-gtr: add board-specific compatible strings

Most arm board have a board-specific compatible string that allows e.g.
userspace to match specific firmware variants or apply specific
policies.

Add board-specific properties to both variants of the Clearfog GTR:
- solidrun,clearfog-gtr-l8
- solidrun,clearfog-gtr-s4

Introduction of a common parent (e.g. "solidrun,clearfog-gtr") is
omitted for brevity.
Since announcement of the two products no additional variants were added
it is assumed that there will always be just two.
Signed-off-by: Josua Mayer <josua@solid-run.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>

arch/arm/boot/dts/marvell/armada-385-clearfog-gtr-l8.dts

@@ -4,6 +4,8 @@
 
 / {
 	model = "SolidRun Clearfog GTR L8";
+	compatible = "solidrun,clearfog-gtr-l8", "marvell,armada385",
+		     "marvell,armada380";
 };
 
 &mdio {

arch/arm/boot/dts/marvell/armada-385-clearfog-gtr-s4.dts

@@ -4,6 +4,8 @@
 
 / {
 	model = "SolidRun Clearfog GTR S4";
+	compatible = "solidrun,clearfog-gtr-s4", "marvell,armada385",
+		     "marvell,armada380";
 };
 
 &sfp0 {