Input: elantech - enable 3rd button support on Fujitsu CELSIUS H780

Input: elantech - enable 3rd button support on Fujitsu CELSIUS H780

Like Fujitsu CELSIUS H760, the H780 also has a three-button Elantech
touchpad, but the driver needs to be told so to enable the middle touchpad
button.

The elantech_dmi_force_crc_enabled quirk was not necessary with the H780.

Also document the fw_version and caps values detected for both H760 and
H780 models.

Signed-off-by: Matti Kurkela <Matti.Kurkela@iki.fi>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>