HID: asus: add support for missing PX series fn keys

commit 831f70a5 upstream.

Add support for missing hotkey keycodes affecting Asus PX13 and PX16 families
so userspace can use them.

Signed-off-by: Amit Chaudhari <amitchaudhari@mac.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>