This is caused by a change in kernel->drivers->usb->serial->options.c , thie fix should be in next kernel
in the meantime, patch attached.
So, this has been working fine for years, in fact still does, despite the latest kernel upgrade from 3.12.x to 3.14.(10|12)
However since using 3.14.x kernel and dmesg are flooded with
option1 ttyUSB0: option_instat_callback: error -2