nfs: encode nfsv4 timestamps as 64-bit

On 32-bit architectures, xdr_encode_nfstime4() needlessly
truncates timestamps to a 32-bit value in the range between
year 1902 and 2038.

Change it to use 'struct timespec64' to allow the entire range
of values supported by the server.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/nfs4xdr.c

@@ -1061,7 +1061,7 @@ static void encode_nfs4_verifier(struct xdr_stream *xdr, const nfs4_verifier *ve
 static __be32 *
 xdr_encode_nfstime4(__be32 *p, const struct timespec64 *t)
 {
-	p = xdr_encode_hyper(p, (__s64)t->tv_sec);
+	p = xdr_encode_hyper(p, t->tv_sec);
 	*p++ = cpu_to_be32(t->tv_nsec);
 	return p;
 }