[jnc_io_usb] align read transfers on max packet size
[jnc_io_usb] align read transfers on max packet size

seems like libusb is having troubles handling arbitrary sized transfers,
at least with Cypress EZ-USB FX2

vovkos/jancy,vovkos/jancy,vovkos/jancy,vovkos/jancy,vovkos/jancy