iwlwifi: mvm: slightly clean up rs_fw_set_supp_rates()

The "supp" variable doesn't need to be unsigned long, only
"tmp" is used with for_each_set_bit(). "supp" should just
be a u16, since that's how it's sent to the firmware.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210205110447.762e50704a39.I014bc7898f90c734f8e9be2a3efaf9bf8b7db6db@changeidSigned-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/rs-fw.c

@@ -248,14 +248,13 @@ static void rs_fw_set_supp_rates(struct ieee80211_sta *sta,
 				 struct iwl_tlc_config_cmd *cmd)
 {
 	int i;
-	unsigned long tmp;
-	unsigned long supp; /* must be unsigned long for for_each_set_bit */
+	u16 supp = 0;
+	unsigned long tmp; /* must be unsigned long for for_each_set_bit */
 	const struct ieee80211_sta_ht_cap *ht_cap = &sta->ht_cap;
 	const struct ieee80211_sta_vht_cap *vht_cap = &sta->vht_cap;
 	const struct ieee80211_sta_he_cap *he_cap = &sta->he_cap;
 
 	/* non HT rates */
-	supp = 0;
 	tmp = sta->supp_rates[sband->band];
 	for_each_set_bit(i, &tmp, BITS_PER_LONG)
 		supp |= BIT(sband->bitrates[i].hw_value);