firewire: Use a buffer fill descriptor for receive when header size is 0.

When the DMA is setup to not strip any headers, we need to use
the buffer fill descriptor instead of the dual buffer, since the
dual buffer descriptor must strip a non-zero number of header quadlets.

Signed-off-by: Kristian Høgsberg <krh@redhat.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>