Make __vunmap static

__vunmap doesn't seem to be used outside of mm/vmalloc.c, and has
no prototype in any header so let's make it static
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/vmalloc.c

@@ -311,7 +311,7 @@ struct vm_struct *remove_vm_area(void *addr)
 	return v;
 }
 
-void __vunmap(void *addr, int deallocate_pages)
+static void __vunmap(void *addr, int deallocate_pages)
 {
 	struct vm_struct *area;