staging: rtl8723au: Use correct struct for WLAN_EID_HT_CAPABILITY

WLAN_EID_HT_CAPABILITY carries a struct ieee80211_ht_operation - use
the right struct instead of a self invented one.

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