mmc: sdhci-of-arasan: Rearrange the platform data structs for modularity

mmc: sdhci-of-arasan: Rearrange the platform data structs for modularity

Existing driver code has the platform specific structures scattered
throughout the driver code. Rearrange the platform specific data
structures for more modularity and readability. This will help in adding
new static functions with more ease.

Signed-off-by: Manish Narani <manish.narani@xilinx.com>
Link: https://lore.kernel.org/r/1586195015-128992-5-git-send-email-manish.narani@xilinx.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>