dt-bindings: mmc: arasan: Update Documentation for the input clock

Add documentation for an optional input clock which is essentially used
in sampling the input data coming from the card.
Signed-off-by: Manish Narani <manish.narani@xilinx.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/arasan,sdhci.txt

@@ -40,9 +40,9 @@ Optional Properties:
   - clock-output-names: If specified, this will be the name of the card clock
     which will be exposed by this device.  Required if #clock-cells is
     specified.
-  - #clock-cells: If specified this should be the value <0>.  With this property
-    in place we will export a clock representing the Card Clock.  This clock
-    is expected to be consumed by our PHY.  You must also specify
+  - #clock-cells: If specified this should be the value <0> or <1>. With this
+    property in place we will export one or two clocks representing the Card
+    Clock. These clocks are expected to be consumed by our PHY.
   - xlnx,fails-without-test-cd: when present, the controller doesn't work when
     the CD line is not connected properly, and the line is not connected
     properly. Test mode can be used to force the controller to function.