net/mlx5: Devcom, extend mlx5_devcom_send_event to work with more than two devices

mlx5_devcom_send_event is used to send event from one eswitch to the
other. In other words, only one event is sent, which means, no error
mechanism is needed.
However, In case devcom have more than two eswitches, a proper error
mechanism is needed. Hence, in case of error, devcom will perform the
error unwind, since devcom knows how many events were successful.

Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>