net/mlx5e: Expose physical layer statistical counters to ethtool

Use ethtool -S to query physical layer statistical counters including:
- rx_symbol_errors_phy: Number of symbol errors that were not corrected
  by FEC correction algorithm or that FEC was not active on this interface.

- rx_corrected_bits_phy: Number of corrected bits according to active
  FEC (RS/FC).

Signed-off-by: Gal Pressman <galp@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>