[SCSI] bfa: Add BSG interface to support ELS, CT and vendor commands.

- Added BSG interface support to BFA driver
- Adds support to send ELS/CT FC passthru commands and
  few vendor specific BSG requests.

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