rtnetlink: catch -EOPNOTSUPP errors from ndo_bridge_getlink

problem reported:
	kernel 4.1.3
	------------
	# bridge vlan
	port	vlan ids
	eth0	 1 PVID Egress Untagged
	 	90
	 	91
	 	92
	 	93
	 	94
	 	95
	 	96
	 	97
	 	98
	 	99
	 	100

	vmbr0	 1 PVID Egress Untagged
	 	94

	kernel 4.2
	-----------
	# bridge vlan
	port	vlan ids

ndo_bridge_getlink can return -EOPNOTSUPP when an interfaces
ndo_bridge_getlink op is set to switchdev_port_bridge_getlink
and CONFIG_SWITCHDEV is not defined. This today can happen to
bond, rocker and team devices. This patch adds -EOPNOTSUPP
checks after calls to ndo_bridge_getlink.

Fixes: 85fdb956 ("switchdev: cut over to new switchdev_port_bridge_getlink")
Reported-by: Alexandre DERUMIER <aderumier@odiso.com>
Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>