greybus: constify the struct device_type usage

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

Signed-off-by: "Ricardo B. Marliere" <ricardo@marliere.net>
Reviewed-by: Alex Elder <elder@linaro.org>
Link: https://lore.kernel.org/r/20240219-device_cleanup-greybus-v1-1-babb3f65e8cc@marliere.net


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>