scsi: Protect SCSI device state changes with a mutex

scsi: Protect SCSI device state changes with a mutex

Serializing SCSI device state changes avoids that two state changes can
occur concurrently, e.g. the state changes in scsi_target_block() and
__scsi_remove_device(). This serialization is essential to make patch
"Make __scsi_remove_device go straight from BLOCKED to DEL" work
reliably.

Enable this mechanism for all scsi_target_*block() callers but not for
the scsi_internal_device_unblock() calls from the mpt3sas driver because
that driver can call scsi_internal_device_unblock() from atomic context.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Orabug: 27546768
(cherry picked from commit 0db6ca8a5e1ea585795db3643ec7d50fc8cb1aff)
Signed-off-by: Kyle Fortin <kyle.fortin@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Conflicts:
	drivers/scsi/scsi_error.c
	drivers/scsi/scsi_lib.c
	include/scsi/scsi_device.h

	Use kmalloc'd state_mutex_kabi in scsi_device to fit new field
	state_mutex in KABI reserved space.