interface and the address allocated, to roll everything back if the
mount fails:
-put an interface pointer into "struct nfs_diskless" to have it
available for cleanup, don't pass it around anymore where the
"struct nfs_diskless" is already passed
-add a "cleanup" function which shuts the interface down
-in the protocol-specific parts, either return with "everything
ready" or "completely shut down"
-use common functions for interface initialization and shutdown
-add a function to delete all routes associate to an interface
(why is this necessary and not done by ~IFF_UP?)
g/c diskless swap stuff
general cleanup
with NFS_BOOT_DHCP.
Don't increment xid between retries anymore, it is not required and
it increases the response time in case of a slow server.
Use common code with bootparam boot.