colibri_t20: fix device-tree compatible node

Use toradex,colibri_t20 as the device-tree compatible node value rather
than toradex,t20 in accordance to our Apalis/Colibri T30 products.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>

arch/arm/dts/tegra20-colibri.dts

@@ -4,7 +4,7 @@
 
 / {
 	model = "Toradex Colibri T20";
-	compatible = "toradex,t20", "nvidia,tegra20";
+	compatible = "toradex,colibri_t20", "nvidia,tegra20";
 
 	chosen {
 		stdout-path = &uarta;