mmc: mmci: add edge support to data and command out in variant data.

This patch adds edge support for data and command out to variant structure
giving more flexibility to the driver to support more SOCs which have
different clock register layout.

Without this patch other new SOCs like Qcom will have to add more code to
special case them

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>