Input: synaptics - add Intertouch support on X1 Carbon 6th and X280

Synaptics devices reported it has Intertouch support,
and it fails via PS/2 as following logs:

psmouse serio2: Failed to reset mouse on synaptics-pt/serio0
psmouse serio2: Failed to enable mouse on synaptics-pt/serio0

Set these new devices to use SMBus to fix this issue, then they report
SMBus version 3 is using, patch:
https://patchwork.kernel.org/patch/9989547/ enabled SMBus ver 3 and
makes synaptics devices work fine on SMBus mode.

Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>