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/drivers/net/wireless/iwlwifi/mvm/rs.c b/drivers/net/wireless/iwlwifi/mvm/rs.c
index 6abf74e..22f1953 100644
--- a/drivers/net/wireless/iwlwifi/mvm/rs.c
+++ b/drivers/net/wireless/iwlwifi/mvm/rs.c
@@ -2815,7 +2815,8 @@
 			      struct ieee80211_sta *sta, void *mvm_sta)
 {
 }
-static struct rate_control_ops rs_mvm_ops = {
+
+static const struct rate_control_ops rs_mvm_ops = {
 	.module = NULL,
 	.name = RS_NAME,
 	.tx_status = rs_tx_status,