Input: synaptics - add Lenovo 80 series ids to SMBus

This time, Lenovo decided to go with different pieces in its latest
series of Thinkpads.

For those we have been able to test:
- the T480 is using Synaptics with an IBM trackpoint
   -> it behaves properly with or without intertouch, there is no point
      not using RMI4
- the X1 Carbon 6th gen is using Synaptics with an IBM trackpoint
   -> the touchpad doesn't behave properly under PS/2 so we have to
      switch it to RMI4 if we do not want to have disappointed users
- the X280 is using Synaptics with an ALPS trackpoint
   -> the recent fixes in the trackpoint handling fixed it so upstream
      now works fine with or without RMI4, and there is no point not
      using RMI4
- the T480s is using an Elan touchpad, so that's a different story

Cc: <stable@vger.kernel.org> # v4.14.x, v4.15.x, v4.16.x
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: KT Liao <kt.liao@emc.com.tw>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/synaptics.c

@@ -172,10 +172,12 @@ static const char * const smbus_pnp_ids[] = {
 	"LEN0048", /* X1 Carbon 3 */
 	"LEN0046", /* X250 */
 	"LEN004a", /* W541 */
+	"LEN0071", /* T480 */
 	"LEN0072", /* X1 Carbon Gen 5 (2017) - Elan/ALPS trackpoint */
 	"LEN0073", /* X1 Carbon G5 (Elantech) */
 	"LEN0092", /* X1 Carbon 6 */
 	"LEN0096", /* X280 */
+	"LEN0097", /* X280 -> ALPS trackpoint */
 	"LEN200f", /* T450s */
 	NULL
 };