ensure we don't use bootconsoles after init has been released

This is a followup to the cleanups for earlyprintk patch from Gerd Hoffmann

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=69331af79cf29e26d1231152a172a1a10c2df511

This ensures that a bootconsole is unregistered if it is not replaced.
The current implementation spews garbage out the bootconsole in this case,
since the bootconsole structure is normally in the init section, and is
freed, but still used.
Signed-off-by: NRobin Getz <rgetz@blackfin.uclinux.org>
Acked-by: NGerd Hoffmann <kraxel@redhat.com>
Acked-by: NPaul Mundt <lethal@linux-sh.org>
Cc: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

kernel/printk.c

@@ -1083,6 +1083,17 @@ int unregister_console(struct console *console)
 }
 EXPORT_SYMBOL(unregister_console);
 
+static int __init disable_boot_consoles(void)
+{
+	if (console_drivers->flags & CON_BOOT) {
+		printk(KERN_INFO "turn off boot console %s%d\n",
+			console_drivers->name, console_drivers->index);
+		return unregister_console(console_drivers);
+	}
+	return 0;
+}
+late_initcall(disable_boot_consoles);
+
 /**
  * tty_write_message - write a message to a certain tty, not just the console.
  * @tty: the destination tty_struct