mmc: sd: Use kobj_to_dev() instead of container_of()

Use kobj_to_dev() instead of container_of()

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Link: https://lore.kernel.org/r/1598230956-58523-1-git-send-email-tiantao6@hisilicon.com


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