docs/memory-barriers.txt: Fix references for DMA*.txt files

Commit 985098a0 ("docs: fix references for DMA*.txt files") missed
fixing memory-barriers.txt file.  This commit applies the change to the
file.
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Link: https://lore.kernel.org/r/20200829082607.3146-2-sj38.park@gmail.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/memory-barriers.txt

@@ -546,8 +546,8 @@ There are certain things that the Linux kernel memory barriers do not guarantee:
 	[*] For information on bus mastering DMA and coherency please read:
 
 	    Documentation/driver-api/pci/pci.rst
-	    Documentation/DMA-API-HOWTO.txt
-	    Documentation/DMA-API.txt
+	    Documentation/core-api/dma-api-howto.rst
+	    Documentation/core-api/dma-api.rst
 
 
 DATA DEPENDENCY BARRIERS (HISTORICAL)
@@ -1932,8 +1932,8 @@ There are some more advanced barrier functions:
      here.
 
      See the subsection "Kernel I/O barrier effects" for more information on
-     relaxed I/O accessors and the Documentation/DMA-API.txt file for more
-     information on consistent memory.
+     relaxed I/O accessors and the Documentation/core-api/dma-api.rst file for
+     more information on consistent memory.
 
  (*) pmem_wmb();