net/mlx5: E-Switch, Split creating fdb tables into smaller chunks

Split esw_create_offloads_fdb_tables() into smaller functions.
This will help maintenance.

Signed-off-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: Maor Dickman <maord@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>