staging: gdm724x: use netdev_err() instead of pr_err()

use netdev_err() which is a message printing function specific for network
devices instead of pr_err(), in function netlink_send().

Signed-off-by: Lourdes Pedrajas <lu@pplo.net>
Link: https://lore.kernel.org/r/20200320003947.31726-1-lu@pplo.net


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>