NFSD fix nfserro errno mismatch

There is mismatch between __be32 and u32 in nfserr and errno.

Reported-by: kbuild test robot <lkp@intel.com>
Fixes: d5e54eeb0e3d ("NFSD add nfs4 inter ssc to nfsd4_copy")
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>