IB/mlx4: Add support for CQ time-stamping

This includes:

* support allocation of CQ with the TIMESTAMP_COMPLETION creation flag.

* add timestamp_mask and hca_core_clock to query_device, reporting the
  number of supported timestamp bits (mask) and the hca_core_clock frequency.

* return hca core clock's offset in query_device vendor's data,
  this is needed in order to read the HCA's core clock.

Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>