Input: synaptics - switch ForcePad detection to PNP IDs

According to Synaptics devices with ForcePads use SYN300D and SYN3014 as
PNP IDs, so let's switch from DMI-bases detection scheme to PNP-based
one, which should be more reliable.

Suggested-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>