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/iwlegacy/4965-rs.c b/drivers/net/wireless/iwlegacy/4965-rs.c
index 4d5e332..cdbfc1d 100644
--- a/drivers/net/wireless/iwlegacy/4965-rs.c
+++ b/drivers/net/wireless/iwlegacy/4965-rs.c
@@ -2807,7 +2807,7 @@
 {
 }
 
-static struct rate_control_ops rs_4965_ops = {
+static const struct rate_control_ops rs_4965_ops = {
 	.module = NULL,
 	.name = IL4965_RS_NAME,
 	.tx_status = il4965_rs_tx_status,