vfio/mlx5: Wake up the reader post of disabling the SAVING migration file

vfio/mlx5: Wake up the reader post of disabling the SAVING migration file

Post of disabling the SAVING migration file, which includes setting the
file state to be MLX5_MIGF_STATE_ERROR, call to wake_up_interruptible()
on its poll_wait member.

This lets any potential reader which is waiting already for data as part
of mlx5vf_save_read() to wake up, recognize the error state and return
with an error.

Post of that we don't need to rely on any other condition to wake up
the reader as of the returning of the SAVE command that was previously
executed, etc.

In addition, this change will simplify error flows (e.g health recovery)
once we'll move to chunk mode and multiple SAVE commands may run in the
STOP_COPY phase as we won't need to rely any more on a SAVE command to
wake-up a potential waiting reader.

Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20230911093856.81910-3-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>