NFSv4.2: mark OFFLOAD_CANCEL MOVEABLE

[ Upstream commit 668135b9 ]

OFFLOAD_CANCEL should be marked MOVEABLE for when we need to move
tasks off a non-functional transport.

Fixes: c975c209 ("NFS send OFFLOAD_CANCEL when COPY killed")
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>