MAINTAIERS: Add John Ogness as printk reviewer

John Ogness has started major rework of the printk code. Add him
as reviewer so that he is aware of all other coming changes and
could influence their integration.

Signed-off-by: Petr Mladek <pmladek@suse.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: John Ogness <john.ogness@linutronix.de>
Link: https://lore.kernel.org/r/20200710094432.19655-1-pmladek@suse.com