mac80211: fix sparse warnings/errors

sparse complains about a shadowed variable, which
we can just rename, and lots of stuff if the API
tracer is enabled, so kick out the tracer code in
a sparse run -- the macros just confuse it.

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