dt-bindings: net: dsa: Fix typo

Fix spelling mistake documenation -> documentation.

Fixes: 5a18bb14c0 ("dt-bindings: net: dsa: Let dsa.txt refer to dsa.yaml")
Signed-off-by: Kurt Kanzenbach <kurt@kmk-computers.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/dsa/dsa.txt

@@ -1,4 +1,4 @@
 Distributed Switch Architecture Device Tree Bindings
 ----------------------------------------------------
 
-See Documentation/devicetree/bindings/net/dsa/dsa.yaml for the documenation.
+See Documentation/devicetree/bindings/net/dsa/dsa.yaml for the documentation.