mmc: sdhci-of-arasan: Fix kernel-doc warnings

Modify code to fix the warnings reported by kernel-doc for better
documentation.
Signed-off-by: Manish Narani <manish.narani@xilinx.com>
Link: https://lore.kernel.org/r/1586195015-128992-7-git-send-email-manish.narani@xilinx.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>