iwlwifi: mvm: don't fail when removing a key from an inexisting sta

The iwl_mvm_remove_sta_key() function handles removing a key when the
sta doesn't exist anymore.  Mistakenly, this was changed to return an
error while fixing another bug.

If the mvm_sta doesn't exist, we continue normally, but just don't try
to remove the igtk key.

Fixes: cd4d23c1ea9b ("iwlwifi: mvm: Fix removal of IGTK")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

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

@@ -3332,18 +3332,15 @@ int iwl_mvm_remove_sta_key(struct iwl_mvm *mvm,
 
 	/* Get the station from the mvm local station table */
 	mvm_sta = iwl_mvm_get_key_sta(mvm, vif, sta);
-	if (!mvm_sta) {
-		IWL_ERR(mvm, "Failed to find station\n");
-		return -EINVAL;
-	}
-	sta_id = mvm_sta->sta_id;
+	if (mvm_sta)
+		sta_id = mvm_sta->sta_id;
 
 	IWL_DEBUG_WEP(mvm, "mvm remove dynamic key: idx=%d sta=%d\n",
 		      keyconf->keyidx, sta_id);
 
-	if (keyconf->cipher == WLAN_CIPHER_SUITE_AES_CMAC ||
-	    keyconf->cipher == WLAN_CIPHER_SUITE_BIP_GMAC_128 ||
-	    keyconf->cipher == WLAN_CIPHER_SUITE_BIP_GMAC_256)
+	if (mvm_sta && (keyconf->cipher == WLAN_CIPHER_SUITE_AES_CMAC ||
+			keyconf->cipher == WLAN_CIPHER_SUITE_BIP_GMAC_128 ||
+			keyconf->cipher == WLAN_CIPHER_SUITE_BIP_GMAC_256))
 		return iwl_mvm_send_sta_igtk(mvm, keyconf, sta_id, true);
 
 	if (!__test_and_clear_bit(keyconf->hw_key_idx, mvm->fw_key_table)) {