ARM: at91/tc: fix typo in the DT document

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: stable <stable@vger.kernel.org> [v3.4]

Documentation/devicetree/bindings/arm/atmel-at91.txt

@@ -8,7 +8,7 @@ PIT Timer required properties:
   shared across all System Controller members.
 
 TC/TCLIB Timer required properties:
-- compatible: Should be "atmel,<chip>-pit".
+- compatible: Should be "atmel,<chip>-tcb".
   <chip> can be "at91rm9200" or "at91sam9x5"
 - reg: Should contain registers location and length
 - interrupts: Should contain all interrupts for the TC block