minstrel_ht: fixed rate mode through debugfs

Found several threads about fixed rate mode in minstrel_ht for test
environments, but no patches for it.

This patch provides such a mode through debugfs.

Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/rc80211_minstrel.h b/net/mac80211/rc80211_minstrel.h
index 0f5a833..5d278ec 100644
--- a/net/mac80211/rc80211_minstrel.h
+++ b/net/mac80211/rc80211_minstrel.h
@@ -78,6 +78,18 @@
 	unsigned int update_interval;
 	unsigned int lookaround_rate;
 	unsigned int lookaround_rate_mrr;
+
+#ifdef CONFIG_MAC80211_DEBUGFS
+	/*
+	 * enable fixed rate processing per RC
+	 *   - write static index to debugfs:ieee80211/phyX/rc/fixed_rate_idx
+	 *   - write -1 to enable RC processing again
+	 *   - setting will be applied on next update
+	 */
+	u32 fixed_rate_idx;
+	struct dentry *dbg_fixed_rate;
+#endif
+
 };
 
 struct minstrel_debugfs_info {