Input: synaptics - enable RMI on HP Envy 13-ad105ng

This laptop (and perhaps other variants of the same model) reports an
SMBus-capable Synaptics touchpad. Everything (including suspend and
resume) works fine when RMI is enabled via the kernel command line, so
let's add it to the whitelist.
Signed-off-by: Yussuf Khalil <dev@pp3345.net>
Link: https://lore.kernel.org/r/20200307213508.267187-1-dev@pp3345.net
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/synaptics.c

@@ -186,6 +186,7 @@ static const char * const smbus_pnp_ids[] = {
 	"SYN3052", /* HP EliteBook 840 G4 */
 	"SYN3221", /* HP 15-ay000 */
 	"SYN323d", /* HP Spectre X360 13-w013dx */
+	"SYN3257", /* HP Envy 13-ad105ng */
 	NULL
 };