net: dpaa2-switch: use extack in dpaa2_switch_port_bridge_join

We need to propagate the extack argument for
dpaa2_switch_port_bridge_join to use it in a future patch, and it looks
like there is already an error message there which is currently printed
to the console. Move it over netlink so it is properly transmitted to
user space.

Cc: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Acked-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>