IB/core: Only enforce security for InfiniBand

For now the only LSM security enforcement mechanism available is
specific to InfiniBand. Bypass enforcement for non-IB link types.

This fixes a regression where modify_qp fails for iWARP because
querying the PKEY returns -EINVAL.

Cc: Paul Moore <paul@paul-moore.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: stable@vger.kernel.org
Reported-by: Potnuri Bharat Teja <bharat@chelsio.com>
Fixes: d291f1a6("IB/core: Enforce PKey security on QPs")
Fixes: 47a2b338("IB/core: Enforce security on management datagrams")
Signed-off-by: Daniel Jurgens <danielj@mellanox.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Tested-by: Potnuri Bharat Teja <bharat@chelsio.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>