nfsd: Add errno mapping for EREMOTEIO

The NFS client can occasionally return EREMOTEIO when signalling issues
with the server.  ...map to NFSERR_IO.

Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Lance Shelton <lance.shelton@hammerspace.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>