mm: pass the vmem_altmap to vmemmap_free

We can just pass this on instead of having to do a radix tree lookup
without proper locking a few levels into the callchain.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

arch/sparc/mm/init_64.c

@@ -2671,7 +2671,8 @@ int __meminit vmemmap_populate(unsigned long vstart, unsigned long vend,
 	return 0;
 }
 
-void vmemmap_free(unsigned long start, unsigned long end)
+void vmemmap_free(unsigned long start, unsigned long end,
+		struct vmem_altmap *altmap)
 {
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */