Input: atmel_mxt_ts - require device properties present when probing

The driver needs help determining whether it is dealing with a touchscreen
or a touchpad, and with button mapping. Previously we supported passing
this data via device properties, and also had DMI lists for Chromebooks
that specified Atmel devices in ACPI, but did not provide enough data
there. Now that chromeos_laptop driver is adjusted to supply necessary
device properties even for ACPI devices, we can drop the DMI tables and
refuse to probe if device properties are not attached to the device.

We use presence of "compatible" property to determine if device properties
are attached to the device or not and rely on chromeos_laptop to re-probe
the device after attaching missing device properties to it.

Reviewed-by: Benson Leung <bleung@chromium.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>