wl12xx: don't explicitly check for unjoined ibss

After the ibss carrier issue was fixed, we can revert
the following patch:

commit 48309fd4
Author: Shahar Lev <shahar@wizery.com>
Date:   Fri Oct 7 18:17:25 2011 +0200

    wl12xx: remove warning message during IBSS Tx

    mac80211 sets the carrier on an IBSS interface even when no network is
    joined. Ignore garbage frames transmitted on a disconnected IBSS
    interface without printing warnings.
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>

drivers/net/wireless/wl12xx/tx.c

@@ -427,15 +427,7 @@ static int wl1271_prepare_tx_frame(struct wl1271 *wl, struct wl12xx_vif *wlvif,
 	}
 	hlid = wl12xx_tx_get_hlid(wl, wlvif, skb);
 	if (hlid == WL12XX_INVALID_LINK_ID) {
-		if (wlvif->bss_type == BSS_TYPE_IBSS &&
-		    !test_bit(WLVIF_FLAG_IBSS_JOINED, &wlvif->flags)) {
-			/* It's ok to drop packets when not joined to IBSS */
-			wl1271_debug(DEBUG_TX, "dropping skb while IBSS not "
-				     " joined");
-		} else {
 		wl1271_error("invalid hlid. dropping skb 0x%p", skb);
-		}
-
 		return -EINVAL;
 	}