firewire: adopt read cycle timer ABI from raw1394

This duplicates the read cycle timer feature of raw1394 (added in Linux
2.6.21) in firewire-core's userspace ABI.  The argument to the ioctl is
reordered though to ensure 32/64 bit compatibility.

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