[SCSI] mpt2sas : Add support for RAID Action System Shutdown Initiated at OS shutdown

(1) Added new function _scsih_ir_shutdown.  This function will issue the
MPI2_RAID_ACTION_SYSTEM_SHUTDOWN_INITIATED request via
MPI2_FUNCTION_RAID_ACTION. The function will wait 10 seconds for reply
message frame, then print out the ioc status and loginfo.  This function is
only called when there are raid volumes present.

(2) Add shutdown callback in the struct pci_driver object scsih_driver. This
will be called only when the system is shutting down. From this function, we
will call _scsih_ir_shutdown mentioned above.

(3) Add support in _scsih_remove to call _scsih_ir_shutdown. The function
_scsih_remove will be called when the driver is unloaded (and system is
still running).

scsih internal command contex is added to send internal message frames
from mpt2sas_scsih.c.

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