Input: synaptics - enable SMBus on ThinkPad E480 and E580

They are capable of using intertouch and it works well with
psmouse.synaptics_intertouch=1, so add them to the list.

Without it, scrolling and gestures are jumpy, three-finger pinch gesture
doesn't work and three- or four-finger swipes sometimes get stuck.

Signed-off-by: Alexander Mikhaylenko <exalm7659@gmail.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>