firewire: ohci: copy_iso_headers(): make comment match the code

The comment incorrectly talked about one little-endian quadlet, while
there are actually two.  Furthermore, the endianness of the remaining
headers depends on whatever protocol is used, so don't mention them.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>