nfs4: Rename nfs41_setup_state_renewal

The function nfs41_setup_state_renewal is useful to the nfs 4.0 client
as well, so rename the function to nfs4_setup_state_renewal.

Signed-off-by: Donald Buczek <buczek@molgen.mpg.de>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>