block, scsi: Fix race between SPI domain validation and system suspend

Avoid that the following warning is reported when suspending a system
that is using the mptspi driver:

WARNING: CPU: 0 PID: 4187 at drivers/scsi/scsi_lib.c:2960 scsi_device_quiesce+0x20/0xb0
EIP: scsi_device_quiesce+0x20/0xb0
Call Trace:
 spi_dv_device+0x65/0x5f0 [scsi_transport_spi]
 mptspi_dv_device+0x4d/0x170 [mptspi]
 mptspi_dv_renegotiate_work+0x49/0xc0 [mptspi]
 process_one_work+0x190/0x2e0
 worker_thread+0x37/0x3f0
 kthread+0xcb/0x100
 ret_from_fork+0x19/0x24

Fixes: 3a0a5299 (block, scsi: Make SCSI quiesce and resume work reliably)
Reported-by: Woody Suwalski <terraluna977@gmail.com>
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
[ rjw : Subject ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>