RDMA/ocrdma: Query and initalize the PFC SL

This patch implements routine to query the PFC priority from the
adapter port.

Following are the changes implemented:

 * A new FW command is implemented to query the operational/admin DCBX
   configuration from the FW and obtain active priority(service
   level).
 * Adds support for the async event reported by FW when the PFC
   priority changes. Service level is re-initialized during modify_qp
   or create_ah, based on this event.
 * Maintain SL value in ocrdma_dev structure and refer that as and
   when needed.

Signed-off-by: Devesh Sharma <devesh.sharma@emulex.com>
Signed-off-by: Selvin Xavier <selvin.xavier@emulex.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>