iwlwifi: correct frequency settings

After commit 59eb21a6
"cfg80211: Extend channel to frequency mapping for 802.11j"
we use uninitialized sband->band when assign channel frequencies, what
results that 5GHz channels have erroneous (zero) center_freq value.

Patch fixes problem and simplifies code a bit.
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-core.c

@@ -219,16 +219,12 @@ int iwlcore_init_geos(struct iwl_priv *priv)
 		if (!is_channel_valid(ch))
 			continue;
 
-		if (is_channel_a_band(ch))
-			sband =  &priv->bands[IEEE80211_BAND_5GHZ];
-		else
-			sband =  &priv->bands[IEEE80211_BAND_2GHZ];
+		sband =  &priv->bands[ch->band];
 
 		geo_ch = &sband->channels[sband->n_channels++];
 
 		geo_ch->center_freq =
-				ieee80211_channel_to_frequency(ch->channel,
-							       sband->band);
+			ieee80211_channel_to_frequency(ch->channel, ch->band);
 		geo_ch->max_power = ch->max_power_avg;
 		geo_ch->max_antenna_gain = 0xff;
 		geo_ch->hw_value = ch->channel;