mac80211: make rate control ops const

Change the code to allow making all the rate control ops
const, nothing ever needs to change them. Also change all
drivers to make use of this and mark the ops const.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/rc80211_pid_algo.c b/net/mac80211/rc80211_pid_algo.c
index 958fad0..d0da2a7 100644
--- a/net/mac80211/rc80211_pid_algo.c
+++ b/net/mac80211/rc80211_pid_algo.c
@@ -452,7 +452,7 @@
 	kfree(priv_sta);
 }
 
-static struct rate_control_ops mac80211_rcpid = {
+static const struct rate_control_ops mac80211_rcpid = {
 	.name = "pid",
 	.tx_status = rate_control_pid_tx_status,
 	.get_rate = rate_control_pid_get_rate,