x86: coral: Fall back to coreboot video when FSP missing

When booting from coreboot the FSP video information is no-longer
available. Enable the coreboot driver so that we can get some sort of
display in this case.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/x86/dts/chromebook_coral.dts

@@ -149,6 +149,11 @@
 		#interrupt-cells = <2>;
 	};
 
+	coreboot-video {
+		/* This will only activate when booted from coreboot */
+		compatible = "coreboot-fb";
+	};
+
 	keyboard {
 		intel,duplicate-por;
 	};