net/mlx5e: E-Switch, Use xarray for devcom paired device index

To allow devcom events on E-Switch that is not a vport group manager,
use vhca id as an index instead of device index which might be shared
between several E-Switches. for example SF and its PF.

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