net/mlx5: E-switch, mark devcom as not ready when all eswitches are unpaired

Whenever an eswitch is unpaired with another, the driver mark devcom
as not ready. While this is correct in case we are pairing only two
eswitches, in order to support pairing of more than two eswitches,
driver need to mark devcom as not ready only when all eswitches are
unpaired.

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>