switchdev: add new switchdev bridge setlink

Add new switchdev_port_bridge_setlink that can be used by drivers
implementing .ndo_bridge_setlink to set switchdev bridge attributes.
Basically turn the raw rtnl_bridge_setlink netlink into switchdev attr
sets.  Proper netlink attr policy checking is done on the protinfo part of
the netlink msg.

Currently, for protinfo, only bridge port attrs BR_LEARNING and
BR_LEARNING_SYNC are parsed and passed to port driver.

For afspec, VLAN objs are passed so switchdev driver can set VLANs assigned
to SELF.  To illustrate with iproute2 cmd, we have:

	bridge vlan add vid 10 dev sw1p1 self master

To add VLAN 10 to port sw1p1 for both the bridge (master) and the device
(self).

Signed-off-by: Scott Feldman <sfeldma@gmail.com>
Acked-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>