bridge: mrp: Extend bridge interface

To integrate MRP into the bridge, first the bridge needs to be aware of ports
that are part of an MRP ring and which rings are on the bridge.
Therefore extend bridge interface with the following:
- add new flag(BR_MPP_AWARE) to the net bridge ports, this bit will be
  set when the port is added to an MRP instance. In this way it knows if
  the frame was received on MRP ring port
- add new flag(BR_MRP_LOST_CONT) to the net bridge ports, this bit will be set
  when the port lost the continuity of MRP Test frames.
- add a list of MRP instances

Reviewed-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>