docs: Fix typo in Documentation/memory-barriers.txt

This commit changes "architecure" to the correct spelling,
"architecture".

Signed-off-by: Stan Drozd <drozdziak1@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Documentation/memory-barriers.txt

@@ -27,7 +27,7 @@ The purpose of this document is twofold:
  (2) to provide a guide as to how to use the barriers that are available.
 
 Note that an architecture can provide more than the minimum requirement
-for any particular barrier, but if the architecure provides less than
+for any particular barrier, but if the architecture provides less than
 that, that architecture is incorrect.
 
 Note also that it is possible that a barrier may be a no-op for an