mlxsw: reg: Add cwtp & cwtpm registers

This patch adds 2 new registers:
 - Congestion WRED ECN TClass Profile Register [CWTP]
 - Congestion WRED ECN TClass and Pool Mapping Register [CWTPM]

These registers would later be needed to offload RED-related
functionality to the HW.

Signed-off-by: Yuval Mintz <yuvalm@mellanox.com>
Signed-off-by: Nogah Frankel <nogahf@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>