Input: edt-ft5x06 - add support for different max support points

Update the code so that the maximum supported points aren't hard coded but
can be changed.

Set the maximum support points based on the data passed along side the
compatible field.

Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>