NFS: Create an init_nfs_v4() function

I want to initialize all of NFS v4 in a single function that will
eventually be used as the v4 module init function.

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>