platform/x86: asus-nb-wmi: Make use of dmi->ident

Make use of dmi->ident as other drivers do, like fujitsu, intel,
hp and samsung.

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>