NFSD: Add an nfsd4_encode_nfstime4() helper

[ Upstream commit 26217679 ]

Clean up: de-duplicate some common code.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Tom Talpey <tom@talpey.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>