net/mlx5e: Avoid query PPCNT register if not supported by the device

PPCNT is not supported if PCAM access reg is supported and ppcnt bit is clear.

Signed-off-by: Eyal Davidovich <eyald@mellanox.com>
Reviewed-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>