scsi: mpt: Move scsi_remove_host() out of mptscsih_remove_host()

Commit c5ce0abe ("scsi: sas: move scsi_remove_host call...")  moved
the call to scsi_remove_host() into sas_remove_host(), but forgot to
modify the mpt drivers.

Fixes: c5ce0abe ("scsi: sas: move scsi_remove_host call into sas_remove_host")
Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>