bridge: mrp: Extend br_mrp_switchdev to detect better the errors

This patch extends the br_mrp_switchdev functions to be able to have a
better understanding what cause the issue and if the SW needs to be used
as a backup.

There are the following cases:
- when the code is compiled without CONFIG_NET_SWITCHDEV. In this case
  return success so the SW can continue with the protocol. Depending
  on the function, it returns 0 or BR_MRP_SW.
- when code is compiled with CONFIG_NET_SWITCHDEV and the driver doesn't
  implement any MRP callbacks. In this case the HW can't run MRP so it
  just returns -EOPNOTSUPP. So the SW will stop further to configure the
  node.
- when code is compiled with CONFIG_NET_SWITCHDEV and the driver fully
  supports any MRP functionality. In this case the SW doesn't need to do
  anything. The functions will return 0 or BR_MRP_HW.
- when code is compiled with CONFIG_NET_SWITCHDEV and the HW can't run
  completely the protocol but it can help the SW to run it. For
  example, the HW can'...