[SCSI] qla2xxx: Handle interrupt registration failures more gracefully.

If interrupt registration failed we could crash the machine as we were trying
to deference some pointers which weren't allocated yet.  Move the allocation
a little earlier and make some checks to the free resource code to make sure
that we don't try to free a resource that was never allocated.

Signed-off-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>