vmalloc: call flush_cache_vunmap() from unmap_kernel_range()

Impact: proper vcache flush on unmap_kernel_range()

flush_cache_vunmap() should be called before pages are unmapped.  Add
a call to it in unmap_kernel_range().
Signed-off-by: Tejun Heo <tj@kernel.org>

mm/vmalloc.c

@@ -1012,6 +1012,8 @@ void __init vmalloc_init(void)
 void unmap_kernel_range(unsigned long addr, unsigned long size)
 {
 	unsigned long end = addr + size;
+
+	flush_cache_vunmap(addr, end);
 	vunmap_page_range(addr, end);
 	flush_tlb_kernel_range(addr, end);
 }