firewire: Add read/write and size annotations to IOC numbers.

Also, with this change, refactor ioctl dispatch code to do the
copying from and to user space as indicated by the IOC annotations.

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