drm/i915: Pass the dma_addr_t array as const to rotate_pages()

rotate_pages() doesn't modify the passed in dma addresses, so make
them const.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1452777736-4909-4-git-send-email-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -3331,7 +3331,7 @@ i915_gem_obj_lookup_or_create_ggtt_vma(struct drm_i915_gem_object *obj,
 }
 
 static struct scatterlist *
-rotate_pages(dma_addr_t *in, unsigned int offset,
+rotate_pages(const dma_addr_t *in, unsigned int offset,
 	     unsigned int width, unsigned int height,
 	     struct sg_table *st, struct scatterlist *sg)
 {