Change return value of the callbacks from void to int. Make
implementations across all drivers return negative errno
values in case of error conditions.
Both callbacks are updated together because a large number of
drivers assign the same function to both callbacks.
Signed-off-by: Igor Romanov <igor.romanov@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>
