staging: rtl8723au: Don't use pktfile interface in rtw_xmitframe_coalesce23a()

The pktfil interface is horrible, no idea where it came from, but not
using it is a win.

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