[SCSI] mpt2sas: Added DID_NO_CONNECT return when driver remove and avoid shutdown call

Driver should not call shutdown call from _scsih_remove otherwise,
The scsi midlayer can be deadlocked when devices are removed from the driver
pci_driver->shutdown handler.

Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>