[SCSI] bfa: Added support to collect and reset fcport stats

- Added support to collect and reset fcport stats.
- Modified design to allow multiple requests for fcport stats.
  - fcport will remember the stats request in its stats_pending
    queue and service each of the queued requests after receiving
    a firmware response for the prior request.

Signed-off-by: Krishna Gudipati <kgudipat@brocade.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>