mac80211: use spin_lock_bh() for tim_lock

There's no need to use _irqsave() as the lock
is never used in interrupt context.

This also fixes a problem in the iwlwifi MVM
driver that calls spin_unlock_bh() within its
set_tim() callback.

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

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

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