dt-bindings: mmc: Correct the type of the clk phase properties

The clock phase properties are having two uint32 values. The minItems
and maxItems are set to 2 for the same. So the property type should be
'uint32-array' and not 'uint32'. Modify it to correct the same.

Reported-by: Rob Herring <robh@kernel.org>
Signed-off-by: Manish Narani <manish.narani@xilinx.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>