staging: panel: Use pr_err(...) rather than printk(KERN_ERR ...)

-Removed unnecessary OOM messages.
-Removed embedded message prefixes.
-Added __func__ to some pr_err messages.
-Converted printk(KERN_ERR to pr_err
-Refactored split printk strings onto a single line
-Removed the space before the '!'.

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