bus: ti-sysc: 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
sysc_device_type variable to be a constant structure 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>
Message-ID: <20240219-device_cleanup-ti-sysc-v1-1-13b53177d0a5@marliere.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>