switchdev: mrp: Remove CONFIG_BRIDGE_MRP

Remove #IS_ENABLED(CONFIG_BRIDGE_MRP) from switchdev.h. This will
simplify the code implements MRP callbacks and will be similar with the
vlan filtering.

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