net: ipv4: Allow UDP packets with broadcast dst address

Make sure we are able to receive UDP packets with broadcast
destination address. If CONFIG_NET_IPV4_ACCEPT_ZERO_BROADCAST
is set, then check here also non-standard broadcast address
that is described in RFC 1122 chapter 3.3.6.

Fixes #11617

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>