printk: reimplement log_cont using record extension

Use the record extending feature of the ringbuffer to implement
continuous messages. This preserves the existing continuous message
behavior.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200914123354.832-7-john.ogness@linutronix.de
1 file changed