armv8: fsl-layerscape: Update README.falcon for compression

Update README.falcon to use "none" for compression property for
ramdisk image to avoid being uncompressed upon loading.

Signed-off-by: York Sun <york.sun@nxp.com>

arch/arm/cpu/armv8/fsl-layerscape/doc/README.falcon

@@ -110,7 +110,7 @@ Example:
 			type = "ramdisk";
 			arch = "arm64";
 			os = "linux";
-			compression = "gzip";
+			compression = "none";
 			load = <0xa0000000>;
 		};
 	};