IB/mlx4: Miscellaneous adjustments for SR-IOV IB support

1. Allow only master to change node description.
2. Prevent AH leakage in send mads.
3. Take device part number from PCI structure, so that guests see the
   VF part number (and not the PF part number).
4. Place the device revision ID into caps structure at startup.
5. SET_PORT in update_gids_task needs to go through wrapper on master.
6. In mlx4_ib_event(), PORT_MGMT_EVENT needs be handled in a work
   queue on the master, since it propagates events to slaves using
   GEN_EQE.
7. Do not support FMR on slaves.
8. Add spinlock to slave_event(), since it is called both in interrupt
   context and in process context (due to 6 above, and also if
   smp_snoop is used).  This fix was found and implemented by Saeed
   Mahameed <saeedm@mellanox.com>

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