staging: rtl8723au: Remove unused rtw_adapter * from struct intf_hdl

struct intf_hdl is now purely a wrapper around struct _io_ops, so we
can get rid of it in the next patch.

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