[SCSI] mpt2sas: Delete volume before HBA detach.

The driver hangs when doing `rmmod mpt2sas` if there are any
IR volumes present.The hang is due the scsi midlayer trying to access the
IR volumes after the driver releases controller resources.  Perhaps when
scsi_remove_host is called,the scsi mid layer is sending some request.
This doesn't occur for bare drives becuase the driver is already reporting
those drives deleted prior to calling mpt2sas_base_detach.
To solve this issue, we need to delete the volumes as well.

Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Reviewed-by: Eric Moore <eric.moore@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>