arm: l2cc: doc: fix device tree example typo

The list of attributes above details the use of the 'filter-ranges'
property, but the example improperly used 'filter-latency'.  Make these
consistent by fixing up the example.

Signed-off-by: Josh Cartwright <josh.cartwright@ni.com>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>

Documentation/devicetree/bindings/arm/l2cc.txt

@@ -37,7 +37,7 @@ L2: cache-controller {
         reg = <0xfff12000 0x1000>;
         arm,data-latency = <1 1 1>;
         arm,tag-latency = <2 2 2>;
-        arm,filter-latency = <0x80000000 0x8000000>;
+        arm,filter-ranges = <0x80000000 0x8000000>;
         cache-unified;
         cache-level = <2>;
 	interrupts = <45>;