iwlwifi: mvm: rs: Remove unused 'mcs' variable

Commit 5fc0f76c introduced Rx stats from debugfs, the function
iwl_mvm_reset_frame_stats from that commit defines and sets mcs but
does not use it. Compiling iwlwifi with W=1 gives this warning -

iwlwifi/mvm/rs.c: In function ‘iwl_mvm_update_frame_stats’:
iwlwifi/mvm/rs.c:3074:14: warning: variable ‘mcs’ set but not used [-Wunused-but-set-variable]

Fixes: 5fc0f76c (iwlwifi: mvm: add Rx frames statistics via debugfs)
Signed-off-by: Kirtika Ruchandani <kirtika@google.com>
Cc: Eyal Shapira <eyal@wizery.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

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

@@ -3065,7 +3065,7 @@ static void iwl_mvm_reset_frame_stats(struct iwl_mvm *mvm)
 
 void iwl_mvm_update_frame_stats(struct iwl_mvm *mvm, u32 rate, bool agg)
 {
-	u8 nss = 0, mcs = 0;
+	u8 nss = 0;
 
 	spin_lock(&mvm->drv_stats_lock);
 
@@ -3093,11 +3093,9 @@ void iwl_mvm_update_frame_stats(struct iwl_mvm *mvm, u32 rate, bool agg)
 
 	if (rate & RATE_MCS_HT_MSK) {
 		mvm->drv_rx_stats.ht_frames++;
-		mcs = rate & RATE_HT_MCS_RATE_CODE_MSK;
 		nss = ((rate & RATE_HT_MCS_NSS_MSK) >> RATE_HT_MCS_NSS_POS) + 1;
 	} else if (rate & RATE_MCS_VHT_MSK) {
 		mvm->drv_rx_stats.vht_frames++;
-		mcs = rate & RATE_VHT_MCS_RATE_CODE_MSK;
 		nss = ((rate & RATE_VHT_MCS_NSS_MSK) >>
 		       RATE_VHT_MCS_NSS_POS) + 1;
 	} else {