Input: add support for Azoteq IQS550/572/525

This patch adds support for the Azoteq IQS550/572/525 family of
trackpad/touchscreen controllers.

The driver has been tested with an IQS550EV02 evaluation board. A
demonstration of the driver's capabilities is available here:

https://youtu.be/sRNNx4XZBts



Signed-off-by: Jeff LaBundy <jeff@labundy.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>