[SCSI] bfa: Add diagnostic port (D-Port) support

- Introduced support for D-Port which is a new port mode during which
  link level diagnostics can be run.
- Provided mechanism to dynamically configure D-Port and initiate diagnostic
  tests to isolate any link level issues.
- In D-Port mode, the HBA port does not participate in fabric or login to the
  remote device or run data traffic.
- Diagnostic tests include running various loopback tests in conjunction with
  the attached device.

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