IB/mlx4: Do not allow APM under RoCE

Automatic Path Migration is not supported under RoCE. Therefore,
return a "not-supported" error if the caller attempts to set an
alternate path in a QP context.

In addition, if there are no IB ports configured, do not report
APM capability in the device flags returned by mlx4_ib_query_device.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>