Force IIO_SENSOR_PROXY_TYPE to iio-buffer-als only for certain Dell models

We are encountering issues, that when enabling some Dell laptops, the readings from iio-poll-als are unstable, or could freeze on certain value. On these systems they have ENV{IIO_SENSOR_PROXY_TYPE}="iio-poll-als iio-buffer-als", and removing iio-poll-als makes reading stable.

This adds workaround to the affected Dell laptop models which may equip with ALS, but I think it is also possible to prefer iio-buffer-als to iio-poll-als when both reading types are available.