NFS: Simplify nfs_request_add_commit_list() arguments

I noticed that all the callers of this function pass cinfo->mds->list as
an argument in addition to the cinfo structure itself.  Let's get rid of
the extra argument, since it doesn't seem to be adding anything.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>