Common nfs_stat_to_errno() is used by both fs/nfs/nfs2xdr.c and
fs/nfs/nfs3xdr.c

Will also be used by fs/nfsd/localio.c
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>