Support for I2C Elan touchpads and pressure range fix

[Paul Kocialkowski]

This series both introduces support for I2C Elan touchpads, thanks to
dmi-independent name-based input device detection and fixes the pressure
range on Elan touchpads (both PS/2 and I2C).

It applies on top of: touchpad: move the pressure range to a hwdb entry
from Peter Hutterer.

The initial problem was discussed in bug:
https://bugs.freedesktop.org/show_bug.cgi?id=100463

This series was tested on various devices, including:
* Chromebook R13 CB5-312T, Acer: I2C touchpad
* Chromebook 13 CB5-311, Acer: I2C touchpad
* Chromebook Flip C100PA, ASUS: I2C touchpad
* G505s, Lenovo: PS/2 touchpad
* N56VB, ASUS: PS/2 touchpad