iwlwifi: include HT configuration when adding stations through rs_rate_init

Driver's first notification of a new station from mac80211 can be through rate
selection API.  This patch fixes a bug where, in this code path, the HT
capabilities of the new station were ignored.

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>