HID: logitech-hidpp: ignore very-short or empty names

Some devices report an empty or very short name, in this case stick
with the name generated by the logitech-dj code instead of overriding it
with e.g. "Logitech ".

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>