[SCSI] bfa: Add support to configure min/max bandwidth for a pcifn

- Added support to configure minimum bandwidth for a pcifn.
- Minimum bandwith is guaranteed at per queue level.
- Added support to update pcifn bandwidth dynamically without
  a server reboot.

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