net/mlx5e: CT: Add ct driver counters

Connection offload is translated to multiple rules over several
hardware flow tables. Unhandled end-cases may cause a hardware
resource leak causing multiple system symptoms such as a host
memory leak, decreased performance and other scale related issues.

Export the current number of firmware FTEs related to the CT table
as a debugfs counter. Also add a dropped packets counter to help
debug packets dropped on restore failure.

To show the offloaded count:
cat /sys/kernel/debug/mlx5/<PCI>/ct_nic/offloaded

To show the dropped count:
cat /sys/kernel/debug/mlx5/<PCI>/ct_nic/rx_dropped

Signed-off-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Roi Dayan <paulb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Reviewed-by: Oz Shlomo <ozsh@nvidia.com>
Reviewed-by: Paul Blakey <paulb@nvidia.com>