scsi: fixup kernel warning during rmmod()

Calling rmmod() on a FC driver will results in warnings like

WARNING: CPU: 60 PID: 14640 at fs/sysfs/group.c:237 device_del+0x54/0x240()
sysfs group ffffffff81eff140 not found for kobject '3:0:0:3'

The problem here is that during scsi_remove_target() we will iterate
over all devices, but fail to remove any of those as the call to
scsi_device_get() fails the check to module_is_live().  Hence the
devices will not be removed at this point, but all intermediate
structures like fc rport etc. will be.  Later on during
scsi_forget_host() the devices are removed for real, but the device
parent is already removed and causes this warning.

Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Kyle Fortin <kyle.fortin@oracle.com>
Tested-by: Don Brace <don.brace@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>