net/mlx5: E-switch, Move vport table functions to a new file

Currently, the vport table functions are in common eswitch offload
file. This file is too big. Move the vport table create, delete and
lookup functions to a separate file. Put the file in esw directory.

Pre-step for generalizing its functionality for serving both the
mirroring and the sample features.

Signed-off-by: Chris Mi <cmi@nvidia.com>
Reviewed-by: Oz Shlomo <ozsh@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>