iwlwifi: remove 60 Mbps from sband bitrates table

ieee80211_supported_band is supposed to only contain legacy rates in the
bitrates table (HT rates go in the ieee80211_sta_ht_cap substruct).  Make
iwlwifi driver obey this restriction by removing the 60 Mbps rate. Also, clean
up a few pieces of other code that formerly relied on 60 Mbps being in
sband->bitrates.

Signed-off-by: Daniel C Halperin <daniel.c.halperin@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn-rs.h

@@ -73,6 +73,7 @@ enum {
 	IWL_RATE_54M_INDEX,
 	IWL_RATE_60M_INDEX,
 	IWL_RATE_COUNT, /*FIXME:RS:change to IWL_RATE_INDEX_COUNT,*/
+	IWL_RATE_COUNT_LEGACY = IWL_RATE_COUNT - 1,	/* Excluding 60M */
 	IWL_RATE_COUNT_3945 = IWL_RATE_COUNT - 1,
 	IWL_RATE_INVM_INDEX = IWL_RATE_COUNT,
 	IWL_RATE_INVALID = IWL_RATE_COUNT,