Since commit aed65af1 ("drivers: make device_type const"), the driver
core can properly handle constant struct device_type. Move the
scsi_host_type, scsi_target_type and scsi_dev_type variables to be constant
structures as well, placing it into read-only memory which can not be
modified at runtime.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Link: https://lore.kernel.org/r/20240219-device_cleanup-scsi-v1-1-c5edf2afe178@marliere.netSigned-off-by: Martin K. Petersen <martin.petersen@oracle.com>