Fix trackpoint configuration on some systems

The path to configure trackpoint devices are not always the same:

* /sys/devices/platform/i8042/serio1/serio2 → with touchpad
* /sys/devices/platform/i8042/serio1 → without (or deactivated) touchpad
* /sys/devices/platform/i8042/serio4/serio5 → ThinkPad X100e, X121e, L520, E145
@lethalman whops, no! :-) fixed it and squashed commits together