net/mlx5e: Refactor RX reporter diagnostics

Break RX diagnostics function into smaller helpers. This enables easier
enhancement in the next patch in the set.

Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>