printk: change message to pr_info

To allow userspace to prevent this message from appearing in the
console by changing the log priority.

This matches other informative messages that the power subsystem emits
when the system changes power states.

Link: http://lkml.kernel.org/r/20180322135833.16602-1-tomeu.vizoso@collabora.com
To: linux-kernel@vger.kernel.org
Cc: kernel@collabora.com
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>