iwlwifi: mvm: clean up invalid station handling

Using IWL_MVM_STATION_COUNT and IWL_INVALID_STATION together
isn't a good idea as they have different values. Always use
IWL_MVM_STATION_COUNT for an invalid station in MVM and move
the definition of the IWL_INVALID_STATION constant into the
DVM driver to avoid making such mistakes again. The one use
in the transport code can be hard-coded to -1 instead as the
station ID is passed as an integer there.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/mvm/tx.c b/drivers/net/wireless/iwlwifi/mvm/tx.c
index c7456af..3fed01e 100644
--- a/drivers/net/wireless/iwlwifi/mvm/tx.c
+++ b/drivers/net/wireless/iwlwifi/mvm/tx.c
@@ -365,7 +365,7 @@
 	if (WARN_ON_ONCE(!mvmsta))
 		return -1;
 
-	if (WARN_ON_ONCE(mvmsta->sta_id == IWL_INVALID_STATION))
+	if (WARN_ON_ONCE(mvmsta->sta_id == IWL_MVM_STATION_COUNT))
 		return -1;
 
 	dev_cmd = iwl_mvm_set_tx_params(mvm, skb, sta, mvmsta->sta_id);