The parameters for ETHTOOL_FLASHDEV include a filename, which ought to
be null-terminated.  Currently the only driver that implements
ethtool_ops::flash_device attempts to add a null terminator if
necessary, but does it wrongly.  Do it in the ethtool core instead.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>