Input: synaptics - enable InterTouch for ThinkPad P1/X1E gen 2

With the new RMI4 F3A support, we're now able to enable full RMI4
support for this model. We also tidy up the comments a bit, as the X1E
is essentially the same computer as the P1.

Acked-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20200930225046.173190-3-Jason@zx2c4.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Author: zx2c4

drivers/input/mouse/synaptics.c

@@ -179,8 +179,9 @@ static const char * const smbus_pnp_ids[] = {
 	"LEN0093", /* T480 */
 	"LEN0096", /* X280 */
 	"LEN0097", /* X280 -> ALPS trackpoint */
-	"LEN0099", /* X1 Extreme 1st */
+	"LEN0099", /* X1 Extreme Gen 1 / P1 Gen 1 */
 	"LEN009b", /* T580 */
+	"LEN0402", /* X1 Extreme Gen 2 / P1 Gen 2 */
 	"LEN200f", /* T450s */
 	"LEN2044", /* L470  */
 	"LEN2054", /* E480 */