message: [trel-dnssd] fix wrong instance name size
  The pointer size was misused as the extended address size. They happen
  to be the same (8 bytes) on 64-bit machines but can cause stack
  overflow on other platforms.
diff: @@ -229,12 +229,12 @@ std::string TrelDnssd::GetTrelInstanceName(void)
  {
  const otExtAddress *extaddr = otLinkGetExtendedAddress(mNcp.GetInstance());
  std::string name;
  - char nameBuf[sizeof(extaddr) * 2 + 1];
  + char nameBuf[sizeof(otExtAddress) * 2 + 1];
  - Utils::Bytes2Hex(extaddr->m8, sizeof(extaddr), nameBuf);
  + Utils::Bytes2Hex(extaddr->m8, sizeof(otExtAddress), nameBuf);
  name = StringUtils::ToLowercase(nameBuf);
  - assert(name.length() == sizeof(extaddr) * 2);
  + assert(name.length() == sizeof(otExtAddress) * 2);
  otbrLogDebug("Using instance name %s", name.c_str());
  return name;
  