In _scsih_probe, propagate the return value from scsi_add_host.
In mpt3sas, avoid calling list_del twice if that returns an
error, which causes list_del corruption warnings if an error
is returned.

Tested with blk-mq and scsi-mq patches to properly cleanup
from and propagate blk_mq_init_rq_map errors.
Signed-off-by: NRobert Elliott <elliott@hp.com>
Acked-by: NSreekanth Reddy <Sreekanth.Reddy@avagotech.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>