dt-bindings: mmc: Remove comment on wakeup-source property

The current comment on wakeup-source is a little confusing because
the word deprecated can be interpreted at first glance to mean that
wakeup-source is deprecated. Also mentioning the obsolete property
confuses more than it helps. Therefore, the comment should be removed
completely because the enable-sdio-wakeup property is not used in
any current DTs. Also remove enable-sdio-wakeup reference in
wakeup-source.txt

Signed-off-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221130121033.7270-1-cniedermaier@dh-electronics.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>