fdts: Fix stdout-path in various platforms

The value of stdout-path is a string and as a result, we can't use a
label as a reference to the serial0 node. This change fixes the
stdout-path property for N1SDP, Morello and TC0 by pointing to the
right alias.
Signed-off-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Change-Id: I3d403389a424569be56327fab4140fec06f96d37

fdts/morello-fvp.dts

@@ -10,7 +10,7 @@
 / {
 
 	chosen {
-		stdout-path = "soc_uart0:115200n8";
+		stdout-path = "serial0:115200n8";
 	};
 
 	reserved-memory {

fdts/n1sdp-single-chip.dts

@@ -16,7 +16,7 @@
 	};
 
 	chosen {
-		stdout-path = "soc_uart0:115200n8";
+		stdout-path = "serial0:115200n8";
 	};
 
 	/* This configuration assumes that standard setup with two DIMM modules.

fdts/tc0.dts

@@ -17,7 +17,7 @@
 	};
 
 	chosen {
-		stdout-path = "soc_uart0:115200n8";
+		stdout-path = "serial0:115200n8";
 	};
 
 	cpus {