ARM: zynq: Use earlycon instead of earlyprintk

Use early console instead of earlyprintk which is supposed to use for
very early debugging (DEBUG_LL).

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/arm/boot/dts/zynq-zed.dts

@@ -29,7 +29,7 @@
 	};
 
 	chosen {
-		bootargs = "earlyprintk";
+		bootargs = "earlycon";
 		stdout-path = "serial0:115200n8";
 	};