netlink.h header have NL_SET_ERR_MSG_MOD that is tied to kmods. We don't
need kmods on bpf tools and this cause compilation error if the header
is included. Fix it by dropping NL_SET_ERR_MSG_MOD.
Link: https://github.com/openwrt/openwrt/pull/11825
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>