bridge: mrp: Update MRP frame type

Replace u16/u32 with be16/be32 in the MRP frame types.
This fixes sparse warnings like:
warning: cast to restricted __be16

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