Input: atmel_mxt_ts - add maxtouch to I2C table for module autoload

The Atmel maxtouch DT binding documents that the compatible string for
the device is "atmel,maxtouch" and the I2C core always reports a module
alias of the form i2c:alias where alias is the compatible string model:

$ grep MODALIAS /sys/devices/platform/12e00000.i2c/i2c-8/8-004b/uevent
MODALIAS=i2c:maxtouch

But there isn't maxtouch entry in the I2C device ID table so when the
i2c:maxtouch MODALIAS uevent is reported, kmod is not able to match the
alias with a module to load:

$ modinfo atmel_mxt_ts | grep alias
alias:          of:N*T*Catmel,maxtouch
alias:          i2c:mXT224
alias:          i2c:atmel_mxt_tp
alias:          i2c:atmel_mxt_ts
alias:          i2c:qt602240_ts

So add the maxtouch entry to the I2C device ID table to allow the module
to be autoloaded when the device is registered via OF.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>