mac80211: remove tracing config symbol

There's little point in this config symbol, if
tracing is disabled the overhead is negligible
and if you think it's too bad you can always
turn off tracing completely.

Also remove the part where we don't have sparse
check the tracing code -- it seems that it can
now deal with it (or the code changed).

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>