Input: elantech - better support all those v2 variants

V2 hardware has many variants. This patch adddresses two issues:

 - some model also has debounce packets, but with a different signature
   than v3. Now we just check debounce for all v2 hardware.

 - due to different scanning methods the hardware uses, x and y ranges have
   to be calculated differently. And for some specific versions, we can just
   see them as custom-made, so set {x, y} the same values as Windows driver
   does.

Signed-off-by: JJ Ding <jj_ding@emc.com.tw>
Tested-by: Richard Schütz <r.schtz@t-online.de>
Reviewed-by: Éric Piel <eric.piel@tremplin-utc.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>