staging: rtl8723au: Fix sparse warnings

Some struct fields in wifi.h are meant to be __le16 but were declared as
unsigned short.  This was reported by sparse:

  rtw_wlan_util.c:538:24: warning: cast to restricted __le16
  rtw_wlan_util.c:1544:29: warning: cast to restricted __le16
  rtw_wlan_util.c:1546:25: warning: cast to restricted __le16

This patch updates the types of the fields in `AC_param` and
`ADDBA_request` structs to be consistent with relevant structs in
include/linux/ieee80211.h.

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