IB/core: Remove smac and vlan id from path record

The GID cache accompanies every GID with attributes.
The GID attributes link the GID with its netdevice, which could be
resolved to smac and vlan id easily. Since we've added the netdevice
(ifindex and net) to the path record, storing the L2 attributes is
duplicated data and hence these attributes are removed.

Signed-off-by: Matan Barak <matanb@mellanox.com>
Reviewed-By: Devesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>