parse: ask for bNumDataRatesSupported data rates
parse: ask for bNumDataRatesSupported data rates

Some devices set bNumDataRatesSupported to a value different from 0 but
libusb_control_transfer() fails if another value (like 256) is used.

The Alcor Micro 9540 is such a reader.

LudovicRousseau/CCID,LudovicRousseau/CCID,LudovicRousseau/CCID