net/mlx5e: Remove mlx5e dependency from E-Switch sample

mlx5/esw/sample.c doesn't really need mlx5e_priv object, we can remove
this redundant dependency by passing the eswitch object directly to
the sample object constructor.

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