NFSv4.2: fix COPY_NOTIFY xdr buf size calculation

[ Upstream commit e8380c2d ]

We need to include sequence size in the compound.

Fixes: 0491567b ("NFS: add COPY_NOTIFY operation")
Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>