Input: elantech - add support for newer elantech touchpads

Newer elantech touchpads are not recognized by the current driver, since it
fails to detect their firmware version number. This prevents more advanced
touchpad features from being usable such as two-finger scrolling. This
patch allows newer touchpads to be detected and be fully functional. Tested
on Sony Vaio SVF13N17PXB.

Signed-off-by: Jordan Rife <jrife0@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>