Input: pixcir_i2c_ts - remove platform data

Previous change moved platform data definition into the driver, making it
unusable for users. Given that we want to move away from custom platform
data structures, and always use device properties (DT, ACPI or static) to
configure devices, let's complete the removal.

Tested-by: Fabio Estevam <festevam@gmail.com>
Tested-by: Michal Vokáč <michal.vokac@ysoft.com>
Reviewed-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>