ieee1394: raw1394: Fix write() for 32bit userland on 64bit kernel

* write(fd, buf, 52) from 32bit app was returning 56.  Most of callers did not
  care, but some (arm registration) did, and anyway it looks bad if request for
  writing 52 bytes returns 56.  And returning sizeof anything in 'int' is not
  good as well.  So all functions now return '0' instead of
  sizeof(struct raw1394_request) on success, and write() itself provides correct
  return value (it just returns value it was asked to write on success as raw1394
  does not do any partial writes at all).

* Related to this was problem that write() could have returned 0 when kernel
  state would become corrupted and moved to different state than
  opened/initialized/connected.  Now it returns -EBADFD which seemed appropriate.

Signed-off-by: Petr Vandrovec <petr@vandrovec.name>
Acked-by: Dan Dennedy <dan@dennedy.org>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> (split into 3 patches)