staging: panel: Use pr_info(...) rather than printk(KERN_INFO

-Added pr_fmt.
-Converted printk(KERN_INFO to pr_info
-Removed embedded message prefixes.

Signed-off-by: Toshiaki Yamane <yamanetoshi@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>