p54: fix sequence no. accounting off-by-one error

P54_HDR_FLAG_DATA_OUT_SEQNR is meant to tell the
firmware that "the frame's sequence number has
already been set by the application."

Whereas IEEE80211_TX_CTL_ASSIGN_SEQ is set for
frames which lack a valid sequence number and
either the driver or firmware has to assign one.

Yup, it's the exact opposite!

Cc: <stable@kernel.org>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/p54/txrx.c

@@ -618,7 +618,7 @@ static void p54_tx_80211_header(struct p54_common *priv, struct sk_buff *skb,
 	else
 		*burst_possible = false;
 
-	if (info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ)
+	if (!(info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ))
 		*flags |= P54_HDR_FLAG_DATA_OUT_SEQNR;
 
 	if (info->flags & IEEE80211_TX_CTL_PSPOLL_RESPONSE)