On targets that provide a reference TinyUSB implementation, like ESP32,
the SDK already defines and implements standard callback functions such
as tud_cdc_line_state_cb(). This causes a symbol clash when enabling
shared implementations like the MicroPython 1200 touch functionality.
To avoid this symbol clash, add an optional macro to allow ports to
use a different function name in the shared implementation.
Signed-off-by: Luca Burelli <l.burelli@arduino.cc>
e0784750aa