Input: synaptics - Lenovo Thinkpad X1 Carbon G5 (2017) with Elantech trackpoints should use RMI

commit 15e2cffec3 upstream.

Lenovo use two different trackpoints in the fifth generation Thinkpad X1
Carbon. Both are accessible over SMBUS/RMI but the pnpIDs are missing.
This patch is for the Elantech trackpoint specifically which also
reports SMB version 3 so rmi_smbus needs to be updated in order to
handle it.

For the record, I was not the first one to come up with this patch as it
has been floating around the internet for a while now. However, I have
spent significant time with testing and my efforts to find the original
author of the patch have been unsuccessful.

Signed-off-by: Edvard Holst <edvard.holst@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/input/mouse/synaptics.c

@@ -173,6 +173,7 @@ static const char * const smbus_pnp_ids[] = {
 	"LEN0046", /* X250 */
 	"LEN004a", /* W541 */
 	"LEN0072", /* X1 Carbon Gen 5 (2017) - Elan/ALPS trackpoint */
+	"LEN0073", /* X1 Carbon G5 (Elantech) */
 	"LEN200f", /* T450s */
 	NULL
 };