SLUB: Deal with annoying gcc warning on kfree()

gcc 4.2 spits out an annoying warning if one casts a const void *
pointer to a void * pointer. No warning is generated if the
conversion is done through an assignment.
Signed-off-by: Christoph Lameter <clameter@sgi.com>

mm/slub.c

@@ -2601,6 +2601,7 @@ EXPORT_SYMBOL(ksize);
 void kfree(const void *x)
 {
 	struct page *page;
+	void *object = (void *)x;
 
 	if (unlikely(ZERO_OR_NULL_PTR(x)))
 		return;
@@ -2610,7 +2611,7 @@ void kfree(const void *x)
 		put_page(page);
 		return;
 	}
-	slab_free(page->slab, page, (void *)x, __builtin_return_address(0));
+	slab_free(page->slab, page, object, __builtin_return_address(0));
 }
 EXPORT_SYMBOL(kfree);