net: Make DEBUG config option naming consistent

Some of the DEBUG config options had _DEBUG string at the
end of the config option. This is inconsistent with the
rest of the networking stack debug options where the _DEBUG
is located in the middle of the option like this
CONFIG_NET_DEBUG_....

Change-Id: I8542079f9a88631e98b417fd6c62d2db48aa9bdf
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>