printk: fix a typo of comment

Fix a typo of comment

Signed-off-by: Wang Honghui <honghui.wang@ucas.com.cn>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/77522C532189E547+Y3yG91g6XALbtdJr@TP-P15V.lan
Link: https://lore.kernel.org/r/0C7C980DB815FAE1+Y3yNXJCqZ3Nzxa5V@TP-P15V.lan