net/mlx5e: Move uplink rep init/cleanup code into own functions

Clean up the code and allows to call uplink rep init/cleanup
from different location later.
To be used later for a new uplink representor mode.

Signed-off-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Eli Britstein <elibr@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>