net: bridge: mrp: Update the Test frames for MRA

According to the standard IEC 62439-2, in case the node behaves as MRA
and needs to send Test frames on ring ports, then these Test frames need
to have an Option TLV and a Sub-Option TLV which has the type AUTO_MGR.

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