console: console handover to preferred console

for earlyprintk=ttyS0,9600 console=tty0 console=ttyS0,9600n8

the handover will happen from earlyser0 to tty0.  but what we want is to
hand over to ttyS0.

Later with serial-convert-early_uart-to-earlycon-for-8250.patch,

	console=tty0 console=uart8250,io,0x3f8,9600n8

will handover to ttyS0 instead of tty0.

Signed-off-by: Yinghai Lu <yinghai.lu@sun.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Gerd Hoffmann <kraxel@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/printk.c

@@ -985,12 +985,15 @@ void register_console(struct console *console)
 	if (!(console->flags & CON_ENABLED))
 		return;
 
-	if (bootconsole) {
+	if (bootconsole && (console->flags & CON_CONSDEV)) {
 		printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
 		       bootconsole->name, bootconsole->index,
 		       console->name, console->index);
 		unregister_console(bootconsole);
 		console->flags &= ~CON_PRINTBUFFER;
+	} else {
+		printk(KERN_INFO "console [%s%d] enabled\n",
+		       console->name, console->index);
 	}
 
 	/*