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>

drivers/input/mouse/synaptics.c

@@ -174,6 +174,8 @@ static const char * const smbus_pnp_ids[] = {
 	"LEN004a", /* W541 */
 	"LEN0072", /* X1 Carbon Gen 5 (2017) - Elan/ALPS trackpoint */
 	"LEN0073", /* X1 Carbon G5 (Elantech) */
+	"LEN0092", /* X1 Carbon 6 */
+	"LEN0096", /* X280 */
 	"LEN200f", /* T450s */
 	NULL
 };