mac80211: removing duplicated parsing of information elements

This patch removes the duplicated parsing of information elements
in ieee80211_rx_bss_info and in ieee_rx_mgmt_beacon

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Ester Kummer <ester.kummer@intel.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>