Fix USB endianness bugs on Linux.

The fields device->idVendor and device->idProduct should not be
converted from little endian to native byteorder, because the
kernel has in fact done so already!

On the other hand, the descriptors read using raw ioctl:s in
register_device() do need to be converted.

Change-Id: I5fe08b626b14ead56a592b68d026690e343c2656