iwlwifi: range checking issue

IWL_RATE_COUNT is 13 and IWL_RATE_COUNT_LEGACY is 12.

IWL_RATE_COUNT_LEGACY is the right one here because iwl3945_rates
doesn't support 60M and also that's how "rates" is defined in
iwlcore_init_geos() from drivers/net/wireless/iwlwifi/iwl-core.c.

        rates = kzalloc((sizeof(struct ieee80211_rate) * IWL_RATE_COUNT_LEGACY),
                        GFP_KERNEL);

Signed-off-by: Dan Carpenter <error27@gmail.com>
Cc: stable@kernel.org
Acked-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>