[SCSI] qla2xxx: Handle change notifications based on switch scan results.

Instead of processing each RSCN individually, use only the name server results
from the switch to tell the existance of a given fcport.

Signed-off-by: Arun Easi <arun.easi@qlogic.com>
Signed-off-by: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>