iwlwifi: mvm: read IWL_RX_MPDU_PHY_SHORT_PREAMBLE only for CCK

Due to a general shortage of RX API bits, the firmware is going
to reuse this bit on non-CCK frames to mean something else. Use
it only on CCK frames to prepare for that change.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

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

@@ -1408,7 +1408,8 @@ void iwl_mvm_rx_mpdu_mq(struct iwl_mvm *mvm, struct napi_struct *napi,
 		rx_status->flag |= RX_FLAG_FAILED_FCS_CRC;
 	}
 	/* set the preamble flag if appropriate */
-	if (phy_info & IWL_RX_MPDU_PHY_SHORT_PREAMBLE)
+	if (rate_n_flags & RATE_MCS_CCK_MSK &&
+	    phy_info & IWL_RX_MPDU_PHY_SHORT_PREAMBLE)
 		rx_status->enc_flags |= RX_ENC_FLAG_SHORTPRE;
 
 	if (likely(!(phy_info & IWL_RX_MPDU_PHY_TSF_OVERLOAD))) {