dt-bindings: mmc: Fix xlnx,mio-bank property values for arasan driver

Xilinx ZynqMP has 3 mio banks and all of them are valid. That's why also
list the first one which is missing. Property is enumeration not range.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/5fa17dfe4b42abefd84b4cbb7b8bcd4d31398f40.1606914986.git.michal.simek@xilinx.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

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

@@ -147,7 +147,7 @@ properties:
 
   xlnx,mio-bank:
     $ref: /schemas/types.yaml#/definitions/uint32
-    enum: [0, 2]
+    enum: [0, 1, 2]
     default: 0
     description:
       The MIO bank number in which the command and data lines are configured.