lldp: lldp_send includes bug

[ehudmarvell]

Hi,

I am enable lldp in my env, after fixing the following bug it seem working
#25084

but while I am using optional lldp fields it isn't.

according to lldp_send:

if (lldp->optional_du && lldp->optional_len) {
if (!net_pkt_write(pkt, (u8_t *)lldp->optional_du,
lldp->optional_len)) {
net_pkt_unref(pkt);
ret = -ENOMEM;
goto out;
}
}

why net_pkt_write with '!' before? if everything good net_pkt_write return 0.
if I remove the '!' it is working fine.

Environment:
Zephyr SDK
Commit SHA :6933248e0cb4f7af31e2bab5b39c594806ab53ac

Thanks,
Ehud