staging: rtl8723au: rtw_cfg80211_inform_bss(): Report the beacon interval already retrieved

Use the beacon interval we already retreived in collect_bss_info()
instead of pulling it out of the saved IE array again.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>