dt-bindings: mmc: Fix unevaluatedProperties warnings in examples

The 'unevaluatedProperties' schema checks is not fully working and doesn't
catch some cases where there's a $ref to another schema. A fix is pending,
but results in new warnings in examples. Fix the warnings by removing
spurious properties or adding a missing property to the schema.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220526014204.2873107-1-robh@kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>