IB/core: When marshaling uverbs path, clear unused fields

IB/core: When marshaling uverbs path, clear unused fields

commit a59c5850f09b4c2d6ad2fc47e5e1be8d654529d6 upstream.

When marsheling a user path to the kernel struct ib_sa_path, need
to zero smac, dmac and set the vlan id to the "no vlan" value.

Fixes: dd5f03beb4f7 ("IB/core: Ethernet L2 attributes in verbs/cm structures")
Reported-by: Aleksey Senin <alekseys@mellanox.com>
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>