iwlwifi: mvm: fix wrong #ifdef that uses a macro from backports

I accidentally pushed a patch with CPTCFG (which is used in the
backports project) to the rs-fw.c file.  Fix that to use CONFIG
instead.

Fixes: 9f66a397 ("iwlwifi: mvm: rs: add ops for the new rate scaling in the FW")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

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

@@ -308,7 +308,7 @@ void iwl_mvm_rs_add_sta(struct iwl_mvm *mvm, struct iwl_mvm_sta *mvmsta)
 	lq_sta->pers.last_rssi = S8_MIN;
 	lq_sta->last_rate_n_flags = 0;
 
-#ifdef CPTCFG_MAC80211_DEBUGFS
+#ifdef CONFIG_MAC80211_DEBUGFS
 	lq_sta->pers.dbg_fixed_rate = 0;
 #endif
 }