When porting the driver to the new libfprint 1.90.0 a mistake was made
where the device was not passed through user_data anymore but it was
still read from there. Stop using user_data in the callback to fix this.
See: #320
When sending static data, it would not be copied. The function that
sends it assumed that it should be free'ed though.
Fix this by simply always making a copy.
Seems like the older uncrustify versions did not find these indentation
issues. Fix them.
Old versions of uncrustify will leave things as is, so this is not a
problem if developers are using an old version of uncrustify.
When a transfer is completed, we automatically unref it since we can't
consider it valid anymore since this point.
Update the drivers not to free the transfer after submitting anymore.
