Since commit aed65af1 ("drivers: make device_type const"), the driver
core can properly handle constant struct device_type. Move the
dsa_device_type, iax_device_type, idxd_wq_device_type, idxd_cdev_file_type,
idxd_cdev_device_type and idxd_group_device_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>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Link: https://lore.kernel.org/r/20240219-device_cleanup-dmaengine-v1-1-9f72f3cf3587@marliere.netSigned-off-by: Vinod Koul <vkoul@kernel.org>