[PATCH] libertas: clean up scan debug messages

* make scan debug output cleaner
* change some LBS_DEB_ASSOC messages to LBS_DEB_SCAN, which is more correct
* move helper functions together
* print function return value in the tracing code at one central location

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Acked-By: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>