staging: comedi: drivers: fix return value of comedi_load_firmware()

staging: comedi: drivers: fix return value of comedi_load_firmware()

commit c6236c0ce39c809c336ca929f68cf8ad02cf94e0 upstream.

Some of the callback functions that upload the firmware in the comedi
drivers return a positive value indicating the number of bytes sent
to the device. Detect this condition and just return '0' to indicate
a successful upload.

Reported-by: Bernd Porr <mail@berndporr.me.uk>
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Ian Abbott <abbotti@mev.co.uk>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>