Input: elantech - enable middle button of touchpad on ThinkPad P72

Input: elantech - enable middle button of touchpad on ThinkPad P72

BugLink: https://bugs.launchpad.net/bugs/1793463
Adding 2 new touchpad IDs to support middle button support.

Cc: stable@vger.kernel.org
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
(cherry picked from commit 91a97507323e1ad4bfc10f4a5922e67cdaf8b3cd linux-next)
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Po-Hsu Lin (Sam) <po-hsu.lin@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>