drm/tests: helpers: Switch to EXPORT_SYMBOL_GPL

drm_kunit_device_init() among other things will allocate a device and
wrap around root_device_register. This function is exported with
EXPORT_SYMBOL_GPL, so we can't really change the license.

Fixes: a77a3ffa ("drm/tests: helpers: Add missing export")
Suggested-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Link: https://lore.kernel.org/r/20221123-rpi-kunit-tests-v3-4-4615a663a84a@cerno.techSigned-off-by: Maxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/tests/drm_kunit_helpers.c

@@ -82,7 +82,7 @@ struct drm_device *drm_kunit_device_init(struct kunit *test, u32 features, char
 
 	return drm;
 }
-EXPORT_SYMBOL(drm_kunit_device_init);
+EXPORT_SYMBOL_GPL(drm_kunit_device_init);
 
 MODULE_AUTHOR("Maxime Ripard <maxime@cerno.tech>");
 MODULE_LICENSE("GPL");