lib/scatterlist.c: fix kunmap() argument in sg_miter_stop()

kunmap() takes as argument the struct page that orginally got kmap()'d,
however the sg_miter_stop() function passed it the kernel virtual address
instead, resulting in weird stuff.

Somehow I ended up fixing this bug by accident while looking for a bug in
the same area.

Reported-by: kerneloops.org
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: <stable@kernel.org>		[2.6.27.x]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

lib/scatterlist.c

@@ -395,7 +395,7 @@ void sg_miter_stop(struct sg_mapping_iter *miter)
 			WARN_ON(!irqs_disabled());
 			kunmap_atomic(miter->addr, KM_BIO_SRC_IRQ);
 		} else
-			kunmap(miter->addr);
+			kunmap(miter->page);
 
 		miter->page = NULL;
 		miter->addr = NULL;