ftdi: Allow re-enumeration of devices and GPIO pins

[maruel]

Currently the ftdi driver can be initialized only once and it cannot re-enumerate any new devices after first initialization. With hot-pluggable USB-devices, this makes it difficult to use the driver, as the application using the driver needs to be restarted.

Please provide a way to trigger re-enumeration of ftdi devices via the d2xx driver.

Migrated from https://github.com/periph/extra/issues/8