Input: elantech - fix detection of touchpad on ASUS s301l

commit 271329b3c798b2102120f5df829071c211ef00ed upstream.

Adjust Elantech signature validation to account fo rnewer models of
touchpads.

Reported-and-tested-by: Màrius Monton <marius.monton@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>