ath9k: match wait_for_completion_timeout return type

Return type of wait_for_completion_timeout is unsigned long not int.
As time_left is exclusively used for wait_for_completion_timeout here its
type is simply changed to unsigned long.

API conformance testing for completions with coccinelle spatches are being
used to locate API usage inconsistencies:
./drivers/net/wireless/ath/ath9k/link.c:197
        int return assigned to unsigned long

Patch was compile tested with x86_64_defconfig + CONFIG_ATH_CARDS=m,

Patch is against 4.1-rc3 (localversion-next is -next-20150514)
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ath/ath9k/link.c

@@ -172,7 +172,7 @@ static bool ath_paprd_send_frame(struct ath_softc *sc, struct sk_buff *skb, int
 	struct ath_hw *ah = sc->sc_ah;
 	struct ath_common *common = ath9k_hw_common(ah);
 	struct ath_tx_control txctl;
-	int time_left;
+	unsigned long time_left;
 
 	memset(&txctl, 0, sizeof(txctl));
 	txctl.txq = sc->tx.txq_map[IEEE80211_AC_BE];