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

Gerd Hoffmann pointed out that my patch from yesterday can lead
to a null pointer dereference if the kernel is booted with no
console, and no earlyprintk defined. This fixes that issue.
Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/printk.c

@@ -1085,11 +1085,13 @@ EXPORT_SYMBOL(unregister_console);
 
 static int __init disable_boot_consoles(void)
 {
+	if (console_drivers != NULL) {
 		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);