bridge: mrp: Update br_mrp to use new return values of br_mrp_switchdev

Check the return values of the br_mrp_switchdev function.
In case of:
- BR_MRP_NONE, return the error to userspace,
- BR_MRP_SW, continue with SW implementation,
- BR_MRP_HW, continue without SW implementation,

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