mac80211: minstrel_ht: fix infinite loop because supported is not being shifted

Currently the for-loop will spin forever if variable supported is
non-zero because supported is never changed.  Fix this by adding in
the missing right shift of supported.

Addresses-Coverity: ("Infinite loop")
Fixes: 48cb39522a ("mac80211: minstrel_ht: improve rate probing for devices with static fallback")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20190822122034.28664-1-colin.king@canonical.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/rc80211_minstrel_ht.c

@@ -634,7 +634,7 @@ minstrel_ht_rate_sample_switch(struct minstrel_priv *mp,
 		u16 supported = mi->supported[g_idx];
 
 		supported >>= mi->max_tp_rate[0] % MCS_GROUP_RATES;
-		for (i = 0; supported; i++) {
+		for (i = 0; supported; supported >>= 1, i++) {
 			if (!(supported & 1))
 				continue;