[SCSI] bfa: Defined a new LPS event to clear virtual link on a vport

Clear virtual links was not propagated upwards to bfa from fw.
This resulted in HBA and switch being in an inconsistent state.

So defined a new LPS event for clear virtual link on a vport,
and also now clear virtual link on a baseport, is sent as a
link down event from the fw.

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