mac80211: use just spin_lock() in ieee80211_get_tkip_p2k()

ieee80211_get_tkip_p2k() may be called with interrupts
disabled, so spin_unlock_bh() isn't safe and leads to
warnings. Since it's always called with BHs disabled
already, just use spin_lock().

Cc: stable@vger.kernel.org
Reported-by: Milan Kocian <milon@wq.cz>
Acked-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/tkip.c

@@ -208,10 +208,10 @@ void ieee80211_get_tkip_p2k(struct ieee80211_key_conf *keyconf,
 	u32 iv32 = get_unaligned_le32(&data[4]);
 	u16 iv16 = data[2] | (data[0] << 8);
 
-	spin_lock_bh(&key->u.tkip.txlock);
+	spin_lock(&key->u.tkip.txlock);
 	ieee80211_compute_tkip_p1k(key, iv32);
 	tkip_mixing_phase2(tk, ctx, iv16, p2k);
-	spin_unlock_bh(&key->u.tkip.txlock);
+	spin_unlock(&key->u.tkip.txlock);
 }
 EXPORT_SYMBOL(ieee80211_get_tkip_p2k);