net/mlx5e: Declare stats groups via macro

net/mlx5e: Declare stats groups via macro

Introduce new macros to declare stats callbacks and groups, for better
code reuse and for individual groups selection per profile which will be
introduced in next patches.

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>