net: marvell: prestera: devlink: add traps/groups implementation

Add devlink traps registration (with corresponding groups) for
all the traffic types that driver traps to the CPU;
prestera_rxtx: report each packet trapped to the CPU (RX) to the
prestera_devlink;

Signed-off-by: Oleksandr Mazur <oleksandr.mazur@plvision.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>