[S390] s390/setup: set default preferred console device "ttyS"

This patch sets the default console device for s390.

The console= kernel parameter can be still used to switch the preferred
console to some other device. In that case, console messages are also
printed on the default console device (ttyS0).
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/setup.c

@@ -740,6 +740,9 @@ static void __init setup_hwcaps(void)
 void __init
 setup_arch(char **cmdline_p)
 {
+	/* set up preferred console */
+	add_preferred_console("ttyS", 0, NULL);
+
         /*
          * print what head.S has found out about the machine
          */