scsi: scsi_transport_fc: refactor event posting routines

There are two routines generating transport events that do the same thing
with only a couple of values set differently.

Refactor so there's a single routine doing the netlink operations to send
the event. All the differences are passed as arguments. Export the symbol
so the generic routine can be called by llds.

Modify the existing two event routines to use the helper.

Signed-off-by: James Smart <jsmart2021@gmail.com>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>