[PATCH: iwn(4)] Fix channel switching in monitor mode

Hi!

 I just got a "Centrino Advanced-N 6230" half-size mini-pcie card
(using iwn6000g2bfw.ko firmware, my Dell Precision M4500 laptop
came with an unsupported Broadcom BCM4313:

	https://laptop.bsdgroup.de/freebsd/index.html?action=show_laptop_detail&laptop=13061

), and found channel switching didn't work in monitor mode, the
patch below seems to fix it - also at:

	http://people.freebsd.org/~nox/tmp/patch-iwn-channel-monitor.txt

 (I also applied the two patches from the `"Intel Centrino Advanced-N +
WiMAX 6250" doesn't work' thread tho I'm not 100% sure they are needed
for this nic:

	http://markmail.org/message/exik7phjs2j7pnsi

and

	http://docs.freebsd.org/cgi/mid.cgi?CAAgh0_bL7K3PZVAZxPV8JwdhnopOvdRp0Z+xHU-CfGba5bz1Kw

)

 And here is the channel switching patch:

--- src/sys/dev/iwn/if_iwn.c.orig
+++ src/sys/dev/iwn/if_iwn.c
_at__at_ -6984,12 +6984,24 _at__at_ iwn_set_channel(struct ieee80211com *ic)
 	const struct ieee80211_channel *c = ic->ic_curchan;
 	struct ifnet *ifp = ic->ic_ifp;
 	struct iwn_softc *sc = ifp->if_softc;
+	int error;
 
 	IWN_LOCK(sc);
 	sc->sc_rxtap.wr_chan_freq = htole16(c->ic_freq);
 	sc->sc_rxtap.wr_chan_flags = htole16(c->ic_flags);
 	sc->sc_txtap.wt_chan_freq = htole16(c->ic_freq);
 	sc->sc_txtap.wt_chan_flags = htole16(c->ic_flags);
+
+	/*
+	 * Only need to set the channel in Monitor mode. AP scanning and auth
+	 * are already taken care of by their respective firmware commands.
+	 */
+	if (ic->ic_opmode == IEEE80211_M_MONITOR) {
+		error = iwn_config(sc);
+		if (error != 0)
+			device_printf(sc->sc_dev,
+			    "error %d settting channel\n", error);
+	}
 	IWN_UNLOCK(sc);
 }