mmc: sdhci-of-arasan: Separate out clk related data to another structure

To improve the code readability, use two different structs, one for
clock provider data and one for mmc platform data.

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