staging: rtl8723au: Remove unnecessary abstraction rtw_os_recv_resource_alloc23a()

No point calling a function to NULL a pointer that was just cleared in
the malloc call.

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