dma-debug: make dma_debug_add_bus take a const pointer

The driver core now can handle a const struct bus_type pointer, and the
dma_debug_add_bus() call just passes on the pointer give to it to the
driver core, so make this pointer const as well to allow everyone to use
read-only struct bus_type pointers going forward.

Cc: Christoph Hellwig <[e-mail]>
Cc: Marek Szyprowski <[e-mail]>
Cc: Robin Murphy <[e-mail]>
Cc: <[e-mail]>
Reviewed-by: Robin Murphy <[e-mail]>
Link: https://lore.kernel.org/r/2023121941-dejected-nugget-681e@gregkh
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

include/linux/dma-map-ops.h

···
 #endif /* CONFIG_ARCH_HAS_TEARDOWN_DMA_OPS */
 
 #ifdef CONFIG_DMA_API_DEBUG
-void dma_debug_add_bus(struct bus_type *bus);
+void dma_debug_add_bus(const struct bus_type *bus);
 void debug_dma_dump_mappings(struct device *dev);
 #else
-static inline void dma_debug_add_bus(struct bus_type *bus)
+static inline void dma_debug_add_bus(const struct bus_type *bus)
 {
 }
 static inline void debug_dma_dump_mappings(struct device *dev)

kernel/dma/debug.c

···
 	return 0;
 }
 
-void dma_debug_add_bus(struct bus_type *bus)
+void dma_debug_add_bus(const struct bus_type *bus)
 {
 	struct notifier_block *nb;