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>