rt61pci: fix NULL pointer dereference in config_lna_gain

commit deee0214 upstream.

We can not pass NULL libconf->conf->channel to rt61pci_config() as it
is dereferenced unconditionally in rt61pci_config_lna_gain() subroutine.

Resolves:
https://bugzilla.kernel.org/show_bug.cgi?id=44361

Reported-and-tested-by: <dolohow@gmail.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/wireless/rt2x00/rt61pci.c

@@ -2243,8 +2243,7 @@ static void rt61pci_txdone(struct rt2x00_dev *rt2x00dev)
 
 static void rt61pci_wakeup(struct rt2x00_dev *rt2x00dev)
 {
-	struct ieee80211_conf conf = { .flags = 0 };
-	struct rt2x00lib_conf libconf = { .conf = &conf };
+	struct rt2x00lib_conf libconf = { .conf = &rt2x00dev->hw->conf };
 
 	rt61pci_config(rt2x00dev, &libconf, IEEE80211_CONF_CHANGE_PS);
 }