firewire-net driver changes:
- fix memory leak and kmap leak at shutdown
- release IR DMA context already at ifdown rather than shutdown
(many controllers have got only 4 of them, so let's not hold it
longer than strictly necessary)
- misc startup/shutdown changes which prepare for later addition
of IPv6-over-1394 support
Signed-off-by: David S. Miller <davem@davemloft.net>