IB/mlx4: Adjust delayed work when a dup is observed

[ Upstream commit 785167a114855c5aa75efca97000e405c2cc85bf ]

When scheduling delayed work to clean up the cache, if the entry already
has been scheduled for deletion, we adjust the delay.

Fixes: 3cf69cc8 ("IB/mlx4: Add CM paravirtualization")
Link: https://lore.kernel.org/r/20200803061941.1139994-7-haakon.bugge@oracle.com


Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>