IB/mad: Delete RMPP_STATE_CANCELING state

The cancel_delayed_work can be called under lock since it doesn't sleep.
This makes the RMPP_STATE_CANCELING state not needed anymore, remove it.

Link: https://lore.kernel.org/r/20200621104738.54850-5-leon@kernel.org


Signed-off-by: Shay Drory <shayd@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>