Some of the networking header files in include/net/ directory were
missing @defgroup doxygen directives.
There was also duplicate @defgroup directives which are now changed
to @addtogroup directives.
Added also missing API links to doc/api/networking.rst file.
Added exceptions to .known-issues/doc/networking.conf file so that
doxygen does not complain.
Jira: ZEP-2308
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Remove NET_UDP_HDR() macro as we cannot safely access UDP header
via it if the network packet header spans over multiple net_buf
fragments.
Fixed also the UDP unit tests so that they pass correctly.
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
