Input: pixcir_i2c_ts - support up to 5 fingers and hardware tracking IDs

Some variants of the Pixcir touch controller support up to 5 simultaneous
fingers and hardware tracking IDs. Prepare the driver for that.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>