staging: asus_oled: Change printk calls to dev_xxx

- Use dev_err whenever a struct device * is present
- None of the printk calls had levels set, but looked like they should
  probably be dev_err

Signed-off-by: Jonathan Brett <jonbrett.dev@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>