net: dsa: remove cross-chip support for MRP

The cross-chip notifiers for MRP are bypass operations, meaning that
even though all switches in a tree are notified, only the switch
specified in the info structure is targeted.

We can eliminate the unnecessary complexity by deleting the cross-chip
notifier logic and calling the ds->ops straight from port.c.

Cc: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>