anv: const-correct anv_{image,buffer}_is_sparse()

I had to do this in a debugging session when I wrote some extra code
to debug sparse issues. I also have a pending patch that will require
this.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28792>

src/intel/vulkan/anv_private.h

@@ -3130,7 +3130,7 @@ struct anv_buffer {
 };
 
 static inline bool
-anv_buffer_is_sparse(struct anv_buffer *buffer)
+anv_buffer_is_sparse(const struct anv_buffer *buffer)
 {
    return buffer->vk.create_flags & VK_BUFFER_CREATE_SPARSE_BINDING_BIT;
 }
@@ -5165,7 +5165,7 @@ struct anv_image {
 };
 
 static inline bool
-anv_image_is_sparse(struct anv_image *image)
+anv_image_is_sparse(const struct anv_image *image)
 {
    return image->vk.create_flags & VK_IMAGE_CREATE_SPARSE_BINDING_BIT;
 }