ARM/dma-mapping: const a pointer to bus_type in arm_iommu_create_mapping()

Change the function arm_iommu_create_mapping() to take a pointer to a
const bus_type as the function does not modify the variable the pointer
points to at all, and the driver core bus functions it calls all expect
a const * type.

Cc: Russell King <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: "Russell King (Oracle)" <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Robin Murphy <[e-mail]>
Cc: Kees Cook <[e-mail]>
Cc: Lukas Bulwahn <[e-mail]>
Cc: Ben Dooks <[e-mail]>
Cc: Linus Walleij <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

arch/arm/include/asm/dma-iommu.h

···
 };
 
 struct dma_iommu_mapping *
-arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, u64 size);
+arm_iommu_create_mapping(const struct bus_type *bus, dma_addr_t base, u64 size);
 
 void arm_iommu_release_mapping(struct dma_iommu_mapping *mapping);
 

arch/arm/mm/dma-mapping.c

···
  * arm_iommu_attach_device function.
  */
 struct dma_iommu_mapping *
-arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, u64 size)
+arm_iommu_create_mapping(const struct bus_type *bus, dma_addr_t base, u64 size)
 {
 	unsigned int bits = size >> PAGE_SHIFT;
 	unsigned int bitmap_size = BITS_TO_LONGS(bits) * sizeof(long);