sll_protocol may be be16

Google's fuzzer platform blows a warning

/src/libwebsockets/lib/plat/unix/unix-sockets.c:497:21: warning: implicit conversion loses integer precision: 'uint32_t' (aka 'unsigned int') to '__be16' (aka 'unsigned short') [-Wimplicit-int-conversion]
  497 |         sll.sll_protocol = (uint32_t)(htons((uint16_t)0x800));

Author: lws-team