typo fixes: occuring -> occurring

Signed-off-by: Adrian Bunk <bunk@stusta.de>
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index cf0d541..28d1bc3 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -602,7 +602,7 @@
 
 This sequence of events is committed to the memory coherence system in an order
 that the rest of the system might perceive as the unordered set of { STORE A,
-STORE B, STORE C } all occuring before the unordered set of { STORE D, STORE E
+STORE B, STORE C } all occurring before the unordered set of { STORE D, STORE E
 }:
 
 	+-------+       :      :