Input: elants - override touchscreen info with DT properties

Allow overriding of information from hardware and support additional
common DT properties like axis inversion. This is required for eg.
Nexus 7 and TF300T where the programmed values in firmware differ
from reality.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
[moved "prop" before DMA buffer]
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Link: https://lore.kernel.org/r/49ea996878264f7c8bde25204e4ddf4b1e85ae71.1587923061.git.mirq-linux@rere.qmqm.pl


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>