bridge: mrp: Extend bridge interface

This patch adds a new flag(BR_MRP_LOST_IN_CONT) to the net bridge
ports. This bit will be set when the port lost the continuity of
MRP_InTest frames.

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