mac80211: remove set but unused variables

Compiling with W=1 found a few variables that are set
but not used (-Wunused-but-set-variable), remove them.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --cc net/mac80211/ibss.c
Simple merge

diff --cc net/mac80211/status.c
Simple merge

diff --cc net/mac80211/util.c
Simple merge