Input: goodix - use max touch number from device config

Use max number of touches from device config instead of hardcoding.

Signed-off-by: Aleksei Mamlin <mamlinav@gmail.com>
Tested-by: Bastien Nocera <hadess@hadess.net>
Acked-by: Bastien Nocera <hadess@hadess.net>
Tested-by: Antonio Ospite <ao2@ao2.it>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>